fetchmail(1) fetchmail reference manual fetchmail(1)
NAME
fetchmail - fetch mail from a POP, IMAP, ETRN, or ODMR-capable server
SYNOPSIS
fetchmail [option...] [mailserver...]
fetchmailconf
DESCRIPTION
fetchmail is a mail-retrieval and forwarding utility; it fetches mail
from remote mailservers and forwards it to your local (client)
machine's delivery system. You can then handle the retrieved mail
using normal mail user agents such as mutt(1), elm(1) or Mail(1). The
fetchmail utility can be run in a daemon mode to repeatedly poll one or
more systems at a specified interval.
The fetchmail program can gather mail from servers supporting any of
the common mail-retrieval protocols: POP2 (legacy, to be removed from
future release), POP3, IMAP2bis, IMAP4, and IMAP4rev1. It can also use
the ESMTP ETRN extension and ODMR. (The RFCs describing all these pro-
tocols are listed at the end of this manual page.)
While fetchmail is primarily intended to be used over on-demand TCP/IP
links (such as SLIP or PPP connections), it may also be useful as a
message transfer agent for sites which refuse for security reasons to
permit (sender-initiated) SMTP transactions with sendmail.
SUPPORT, TROUBLESHOOTING
For troubleshooting, tracing and debugging, you need to increase fetch-
mail's verbosity to actually see what happens. To do that, please run
both of the two following commands, adding all of the options you'd
normally use.
env LC_ALL=C fetchmail -V -v --nodetach --nosyslog
(This command line prints in English how fetchmail understands
your configuration.)
env LC_ALL=C fetchmail -vvv --nodetach --nosyslog
(This command line actually runs fetchmail with verbose English
output.)
Also see item #G3 in fetchmail's FAQ <http://fetchmail.berlios.de/
fetchmail-FAQ.html#G3>
You can omit the LC_ALL=C part above if you want output in the local
language (if supported). However if you are posting to mailing lists,
please leave it in. The maintainers do not necessarily understand your
language, please use English.
CONCEPTS
If fetchmail is used with a POP or an IMAP server (but not with ETRN or
ODMR), it has two fundamental modes of operation for each user account
from which it retrieves mail: singledrop- and multidrop-mode.
In singledrop-mode,
fetchmail assumes that all messages in the user's account (mail-
box) are intended for a single recipient. The identity of the
recipient will either default to the local user currently exe-
cuting fetchmail, or will need to be explicitly specified in the
configuration file.
fetchmail uses singledrop-mode when the fetchmailrc configura-
tion contains at most a single local user specification for a
given server account.
In multidrop-mode,
fetchmail assumes that the mail server account actually contains
mail intended for any number of different recipients. There-
fore, fetchmail must attempt to deduce the proper "envelope
recipient" from the mail headers of each message. In this mode
of operation, fetchmail almost resembles a mail transfer agent
(MTA).
Note that neither the POP nor IMAP protocols were intended for
use in this fashion, and hence envelope information is often not
directly available. The ISP must stores the envelope informa-
tion in some message header and. The ISP must also store one
copy of the message per recipient. If either of the conditions
is not fulfilled, this process is unreliable, because fetchmail
must then resort to guessing the true envelope recipient(s) of a
message. This usually fails for mailing list messages and Bcc:d
mail, or mail for multiple recipients in your domain.
fetchmail uses multidrop-mode when more than one local user
and/or a wildcard is specified for a particular server account
in the configuration file.
In ETRN and ODMR modes,
these considerations do not apply, as these protocols are based
on SMTP, which provides explicit envelope recipient information.
These protocols always support multiple recipients.
As each message is retrieved, fetchmail normally delivers it via SMTP
to port 25 on the machine it is running on (localhost), just as though
it were being passed in over a normal TCP/IP link. fetchmail provides
the SMTP server with an envelope recipient derived in the manner
described previously. The mail will then be delivered according to
your MTA's rules (the Mail Transfer Agent is usually sendmail(8),
exim(8), or postfix(8)). Invoking your system's MDA (Mail Delivery
Agent) is the duty of your MTA. All the delivery-control mechanisms
(such as .forward files) normally available through your system MTA and
local delivery agents will therefore be applied as usual.
If your fetchmail configuration sets a local MDA (see the --mda
option), it will be used directly instead of talking SMTP to port 25.
If the program fetchmailconf is available, it will assist you in set-
ting up and editing a fetchmailrc configuration. It runs under the X
window system and requires that the language Python and the Tk toolkit
(with Python bindings) be present on your system. If you are first
setting up fetchmail for single-user mode, it is recommended that you
use Novice mode. Expert mode provides complete control of fetchmail
configuration, including the multidrop features. In either case, the
'Autoprobe' button will tell you the most capable protocol a given
mailserver supports, and warn you of potential problems with that
server.
GENERAL OPERATION
The behavior of fetchmail is controlled by command-line options and a
run control file, ~/.fetchmailrc, the syntax of which we describe in a
later section (this file is what the fetchmailconf program edits).
Command-line options override ~/.fetchmailrc declarations.
Each server name that you specify following the options on the command
line will be queried. If you don't specify any servers on the command
line, each 'poll' entry in your ~/.fetchmailrc file will be queried.
To facilitate the use of fetchmail in scripts and pipelines, it returns
an appropriate exit code upon termination -- see EXIT CODES below.
The following options modify the behavior of fetchmail. It is seldom
necessary to specify any of these once you have a working .fetchmailrc
file set up.
Almost all options have a corresponding keyword which can be used to
declare them in a .fetchmailrc file.
Some special options are not covered here, but are documented instead
in sections on AUTHENTICATION and DAEMON MODE which follow.
General Options
-? | --help
Displays option help.
-V | --version
Displays the version information for your copy of fetchmail. No
mail fetch is performed. Instead, for each server specified,
all the option information that would be computed if fetchmail
were connecting to that server is displayed. Any non-printables
in passwords or other string names are shown as backslashed C-
like escape sequences. This option is useful for verifying that
your options are set the way you want them.
-c | --check
Return a status code to indicate whether there is mail waiting,
without actually fetching or deleting mail (see EXIT CODES
below). This option turns off daemon mode (in which it would be
useless). It doesn't play well with queries to multiple sites,
and doesn't work with ETRN or ODMR. It will return a false pos-
itive if you leave read but undeleted mail in your server mail-
box and your fetch protocol can't tell kept messages from new
ones. This means it will work with IMAP, not work with POP2,
and may occasionally flake out under POP3.
-s | --silent
Silent mode. Suppresses all progress/status messages that are
normally echoed to standard output during a fetch (but does not
suppress actual error messages). The --verbose option overrides
this.
-v | --verbose
Verbose mode. All control messages passed between fetchmail and
the mailserver are echoed to stdout. Overrides --silent. Dou-
bling this option (-v -v) causes extra diagnostic information to
be printed.
--nosoftbounce
(since v6.3.10, Keyword: set no softbounce, since v6.3.10)
Hard bounce mode. All permanent delivery errors cause messages
to be deleted from the upstream server, see "no softbounce"
below.
--softbounce
(since v6.3.10, Keyword: set softbounce, since v6.3.10)
Soft bounce mode. All permanent delivery errors cause messages
to be left on the upstream server if the protocol supports that.
Default to match historic fetchmail documentation, to be changed
to hard bounce mode in the next fetchmail release.
Disposal Options
-a | --all | (since v6.3.3) --fetchall
(Keyword: fetchall, since v3.0)
Retrieve both old (seen) and new messages from the mailserver.
The default is to fetch only messages the server has not marked
seen. Under POP3, this option also forces the use of RETR
rather than TOP. Note that POP2 retrieval behaves as though
--all is always on (see RETRIEVAL FAILURE MODES below) and this
option does not work with ETRN or ODMR. While the -a and --all
command-line and fetchall rcfile options have been supported for
a long time, the --fetchall command-line option was added in
v6.3.3.
-k | --keep
(Keyword: keep)
Keep retrieved messages on the remote mailserver. Normally,
messages are deleted from the folder on the mailserver after
they have been retrieved. Specifying the keep option causes
retrieved messages to remain in your folder on the mailserver.
This option does not work with ETRN or ODMR. If used with POP3,
it is recommended to also specify the --uidl option or uidl key-
word.
-K | --nokeep
(Keyword: nokeep)
Delete retrieved messages from the remote mailserver. This
option forces retrieved mail to be deleted. It may be useful if
you have specified a default of keep in your .fetchmailrc. This
option is forced on with ETRN and ODMR.
-F | --flush
(Keyword: flush)
POP3/IMAP only. This is a dangerous option and can cause mail
loss when used improperly. It deletes old (seen) messages from
the mailserver before retrieving new messages. Warning: This
can cause mail loss if you check your mail with other clients
than fetchmail, and cause fetchmail to delete a message it had
never fetched before. It can also cause mail loss if the mail
server marks the message seen after retrieval (IMAP2 servers).
You should probably not use this option in your configuration
file. If you use it with POP3, you must use the 'uidl' option.
What you probably want is the default setting: if you don't
specify '-k', then fetchmail will automatically delete messages
after successful delivery.
--limitflush
POP3/IMAP only, since version 6.3.0. Delete oversized messages
from the mailserver before retrieving new messages. The size
limit should be separately specified with the --limit option.
This option does not work with ETRN or ODMR.
Protocol and Query Options
-p <proto> | --proto <proto> | --protocol <proto>
(Keyword: proto[col])
Specify the protocol to use when communicating with the remote
mailserver. If no protocol is specified, the default is AUTO.
proto may be one of the following:
AUTO Tries IMAP, POP3, and POP2 (skipping any of these for
which support has not been compiled in).
POP2 Post Office Protocol 2 (legacy, to be removed from future
release)
POP3 Post Office Protocol 3
APOP Use POP3 with old-fashioned MD5-challenge authentication.
Considered not resistant to man-in-the-middle attacks.
RPOP Use POP3 with RPOP authentication.
KPOP Use POP3 with Kerberos V4 authentication on port 1109.
SDPS Use POP3 with Demon Internet's SDPS extensions.
IMAP IMAP2bis, IMAP4, or IMAP4rev1 (fetchmail automatically
detects their capabilities).
ETRN Use the ESMTP ETRN option.
ODMR Use the the On-Demand Mail Relay ESMTP profile.
All these alternatives work in basically the same way (communicating
with standard server daemons to fetch mail already delivered to a mail-
box on the server) except ETRN and ODMR. The ETRN mode allows you to
ask a compliant ESMTP server (such as BSD sendmail at release 8.8.0 or
higher) to immediately open a sender-SMTP connection to your client
machine and begin forwarding any items addressed to your client machine
in the server's queue of undelivered mail. The ODMR mode requires an
ODMR-capable server and works similarly to ETRN, except that it does
not require the client machine to have a static DNS.
-U | --uidl
(Keyword: uidl)
Force UIDL use (effective only with POP3). Force client-side
tracking of 'newness' of messages (UIDL stands for "unique ID
listing" and is described in RFC1939). Use with 'keep' to use a
mailbox as a baby news drop for a group of users. The fact that
seen messages are skipped is logged, unless error logging is
done through syslog while running in daemon mode. Note that
fetchmail may automatically enable this option depending on
upstream server capabilities. Note also that this option may be
removed and forced enabled in a future fetchmail version. See
also: --idfile.
--idle (since 6.3.3)
(Keyword: idle, since before 6.0.0)
Enable IDLE use (effective only with IMAP). Note that this works
with only one folder at a given time. While the idle rcfile
keyword had been supported for a long time, the --idle command-
line option was added in version 6.3.3. IDLE use means that
fetchmail tells the IMAP server to send notice of new messages,
so they can be retrieved sooner than would be possible with reg-
ular polls.
-P <portnumber> | --service <servicename>
(Keyword: service) Since version 6.3.0.
The service option permits you to specify a service name to con-
nect to. You can specify a decimal port number here, if your
services database lacks the required service-port assignments.
See the FAQ item R12 and the --ssl documentation for details.
This replaces the older --port option.
--port <portnumber>
(Keyword: port)
Obsolete version of --service that does not take service names.
Note: this option may be removed from a future version.
--principal <principal>
(Keyword: principal)
The principal option permits you to specify a service principal
for mutual authentication. This is applicable to POP3 or IMAP
with Kerberos 4 authentication only. It does not apply to Ker-
beros 5 or GSSAPI. This option may be removed in a future
fetchmail version.
-t <seconds> | --timeout <seconds>
(Keyword: timeout)
The timeout option allows you to set a server-nonresponse time-
out in seconds. If a mailserver does not send a greeting mes-
sage or respond to commands for the given number of seconds,
fetchmail will drop the connection to it. Without such a time-
out fetchmail might hang until the TCP connection times out,
trying to fetch mail from a down host, which may be very long.
This would be particularly annoying for a fetchmail running in
the background. There is a default timeout which fetchmail -V
will report. If a given connection receives too many timeouts
in succession, fetchmail will consider it wedged and stop retry-
ing. The calling user will be notified by email if this hap-
pens.
Beginning with fetchmail 6.3.10, the SMTP client uses the recom-
mended minimum timeouts from RFC-5321 while waiting for the
SMTP/LMTP server it is talking to. You can raise the timeouts
even more, but you cannot shorten them. This is to avoid a
painful situation where fetchmail has been configured with a
short timeout (a minute or less), ships a long message (many
MBytes) to the local MTA, which then takes longer than timeout
to respond "OK", which it eventually will; that would mean the
mail gets delivered properly, but fetchmail cannot notice it and
will thus refetch this big message over and over again.
--plugin <command>
(Keyword: plugin)
The plugin option allows you to use an external program to
establish the TCP connection. This is useful if you want to use
ssh, or need some special firewalling setup. The program will
be looked up in $PATH and can optionally be passed the hostname
and port as arguments using "%h" and "%p" respectively (note
that the interpolation logic is rather primitive, and these
tokens must be bounded by whitespace or beginning of string or
end of string). Fetchmail will write to the plugin's stdin and
read from the plugin's stdout.
--plugout <command>
(Keyword: plugout)
Identical to the plugin option above, but this one is used for
the SMTP connections.
-r <name> | --folder <name>
(Keyword: folder[s])
Causes a specified non-default mail folder on the mailserver (or
comma-separated list of folders) to be retrieved. The syntax of
the folder name is server-dependent. This option is not avail-
able under POP3, ETRN, or ODMR.
--tracepolls
(Keyword: tracepolls)
Tell fetchmail to poll trace information in the form 'polling
account %s' and 'folder %s' to the Received line it generates,
where the %s parts are replaced by the user's remote name, the
poll label, and the folder (mailbox) where available (the
Received header also normally includes the server's true name).
This can be used to facilitate mail filtering based on the
account it is being received from. The folder information is
written only since version 6.3.4.
--ssl (Keyword: ssl)
Causes the connection to the mail server to be encrypted via
SSL, by negotiating SSL directly after connecting (SSL-wrapped
mode). It is highly recommended to use --sslcertck to validate
the certificates presented by the server. Please see the
description of --sslproto below! More information is available
in the README.SSL file that ships with fetchmail.
Note that even if this option is omitted, fetchmail may still
negotiate SSL in-band for POP3 or IMAP, through the STLS or
STARTTLS feature. You can use the --sslproto option to modify
that behavior.
If no port is specified, the connection is attempted to the well
known port of the SSL version of the base protocol. This is
generally a different port than the port used by the base proto-
col. For IMAP, this is port 143 for the clear protocol and port
993 for the SSL secured protocol; for POP3, it is port 110 for
the clear text and port 995 for the encrypted variant.
If your system lacks the corresponding entries from /etc/ser-
vices, see the --service option and specify the numeric port
number as given in the previous paragraph (unless your ISP had
directed you to different ports, which is uncommon however).
--sslcert <name>
(Keyword: sslcert)
For certificate-based client authentication. Some SSL encrypted
servers require client side keys and certificates for authenti-
cation. In most cases, this is optional. This specifies the
location of the public key certificate to be presented to the
server at the time the SSL session is established. It is not
required (but may be provided) if the server does not require
it. It may be the same file as the private key (combined key
and certificate file) but this is not recommended. Also see
--sslkey below.
NOTE: If you use client authentication, the user name is fetched
from the certificate's CommonName and overrides the name set
with --user.
--sslkey <name>
(Keyword: sslkey)
Specifies the file name of the client side private SSL key.
Some SSL encrypted servers require client side keys and certifi-
cates for authentication. In most cases, this is optional.
This specifies the location of the private key used to sign
transactions with the server at the time the SSL session is
established. It is not required (but may be provided) if the
server does not require it. It may be the same file as the pub-
lic key (combined key and certificate file) but this is not rec-
ommended.
If a password is required to unlock the key, it will be prompted
for at the time just prior to establishing the session to the
server. This can cause some complications in daemon mode.
Also see --sslcert above.
--sslproto <value>
(Keyword: sslproto)
This option has a dual use, out of historic fetchmail behaviour.
It controls both the SSL/TLS protocol version and, if --ssl is
not specified, the STARTTLS behaviour (upgrading the protocol to
an SSL or TLS connection in-band). Some other options may how-
ever make TLS mandatory.
Only if this option and --ssl are both missing for a poll, there will
be opportunistic TLS for POP3 and IMAP, where fetchmail will attempt to
upgrade to TLSv1 or newer.
Recognized values for --sslproto are given below. You should normally
chose one of the auto-negotiating options, i. e. 'auto' or one of the
options ending in a plus (+) character. Note that depending on OpenSSL
library version and configuration, some options cause run-time errors
because the requested SSL or TLS versions are not supported by the par-
ticular installed OpenSSL library.
'', the empty string
Disable STARTTLS. If --ssl is given for the same server,
log an error and pretend that 'auto' had been used
instead.
'auto' (default). Require TLS. Auto-negotiate TLSv1 or newer,
disable SSLv3 downgrade. (previous releases of fetchmail
have auto-negotiated all protocols that their OpenSSL
library supported, including the broken SSLv3).
'SSL23'
see 'auto'.
'SSL2' Require SSLv2 exactly. SSLv2 is broken, not supported on
all systems, avoid it if possible. This will make fetch-
mail negotiate SSLv2 only, and is the only way to have
fetchmail permit SSLv2.
'SSL3' Require SSLv3 exactly. SSLv3 is broken, not supported on
all systems, avoid it if possible. This will make fetch-
mail negotiate SSLv3 only, and is the only way besides
'SSL3+' to have fetchmail permit SSLv3.
'SSL3+'
same as 'auto', but permit SSLv3 as well. This is the
only way besides 'SSL3' to have fetchmail permit SSLv3.
'TLS1' Require TLSv1. This does not negotiate TLSv1.1 or newer,
and is discouraged. Replace by TLS1+ unless the latter
chokes your server.
'TLS1+'
See 'auto'.
'TLS1.1'
Require TLS v1.1 exactly.
'TLS1.1+'
Require TLS. Auto-negotiate TLSv1.1 or newer.
'TLS1.2'
Require TLS v1.2 exactly.
'TLS1.2+'
Require TLS. Auto-negotiate TLSv1.2 or newer.
Unrecognized parameters
are treated the same as 'auto'.
NOTE: you should hardly ever need to use anything other than ''
(to force an unencrypted connection) or 'auto' (to enforce TLS).
--sslcertck
(Keyword: sslcertck)
Causes fetchmail to require that SSL/TLS be used and disconnect
if it can not successfully negotiate SSL or TLS, or if it cannot
successfully verify and validate the certificate and follow it
to a trust anchor (or trusted root certificate). The trust
anchors are given as a set of local trusted certificates (see
the sslcertfile and sslcertpath options). If the server certifi-
cate cannot be obtained or is not signed by one of the trusted
ones (directly or indirectly), fetchmail will disconnect,
regardless of the sslfingerprint option.
Note that CRL (certificate revocation lists) are only supported
in OpenSSL 0.9.7 and newer! Your system clock should also be
reasonably accurate when using this option.
Note that this optional behavior may become default behavior in
future fetchmail versions.
--sslcertfile <file>
(Keyword: sslcertfile, since v6.3.17)
Sets the file fetchmail uses to look up local certificates. The
default is empty. This can be given in addition to --sslcert-
path below, and certificates specified in --sslcertfile will be
processed before those in --sslcertpath. The option can be used
in addition to --sslcertpath.
The file is a text file. It contains the concatenation of
trusted CA certificates in PEM format.
Note that using this option will suppress loading the default
SSL trusted CA certificates file unless you set the environment
variable FETCHMAIL_INCLUDE_DEFAULT_X509_CA_CERTS to a non-empty
value.
--sslcertpath <directory>
(Keyword: sslcertpath)
Sets the directory fetchmail uses to look up local certificates.
The default is your OpenSSL default directory. The directory
must be hashed the way OpenSSL expects it - every time you add
or modify a certificate in the directory, you need to use the
c_rehash tool (which comes with OpenSSL in the tools/ subdirec-
tory). Also, after OpenSSL upgrades, you may need to run
c_rehash; particularly when upgrading from 0.9.X to 1.0.0.
This can be given in addition to --sslcertfile above, which see
for precedence rules.
Note that using this option will suppress adding the default SSL
trusted CA certificates directory unless you set the environment
variable FETCHMAIL_INCLUDE_DEFAULT_X509_CA_CERTS to a non-empty
value.
--sslcommonname <common name>
(Keyword: sslcommonname; since v6.3.9)
Use of this option is discouraged. Before using it, contact the
administrator of your upstream server and ask for a proper SSL
certificate to be used. If that cannot be attained, this option
can be used to specify the name (CommonName) that fetchmail
expects on the server certificate. A correctly configured
server will have this set to the hostname by which it is
reached, and by default fetchmail will expect as much. Use this
option when the CommonName is set to some other value, to avoid
the "Server CommonName mismatch" warning, and only if the
upstream server can't be made to use proper certificates.
--sslfingerprint <fingerprint>
(Keyword: sslfingerprint)
Specify the fingerprint of the server key (an MD5 hash of the
key) in hexadecimal notation with colons separating groups of
two digits. The letter hex digits must be in upper case. This is
the default format OpenSSL uses, and the one fetchmail uses to
report the fingerprint when an SSL connection is established.
When this is specified, fetchmail will compare the server key
fingerprint with the given one, and the connection will fail if
they do not match regardless of the sslcertck setting. The con-
nection will also fail if fetchmail cannot obtain an SSL cer-
tificate from the server. This can be used to prevent man-in-
the-middle attacks, but the finger print from the server needs
to be obtained or verified over a secure channel, and certainly
not over the same Internet connection that fetchmail would use.
Using this option will prevent printing certificate verification
errors as long as --sslcertck is unset.
To obtain the fingerprint of a certificate stored in the file
cert.pem, try:
openssl x509 -in cert.pem -noout -md5 -fingerprint
For details, see x509(1ssl).
Delivery Control Options
-S <hosts> | --smtphost <hosts>
(Keyword: smtp[host])
Specify a hunt list of hosts to forward mail to (one or more
hostnames, comma-separated). Hosts are tried in list order; the
first one that is up becomes the forwarding target for the cur-
rent run. If this option is not specified, 'localhost' is used
as the default. Each hostname may have a port number following
the host name. The port number is separated from the host name
by a slash; the default port is "smtp". If you specify an abso-
lute path name (beginning with a /), it will be interpreted as
the name of a UNIX socket accepting LMTP connections (such as is
supported by the Cyrus IMAP daemon) Example:
--smtphost server1,server2/2525,server3,/var/imap/socket/lmtp
This option can be used with ODMR, and will make fetchmail a
relay between the ODMR server and SMTP or LMTP receiver.
--fetchdomains <hosts>
(Keyword: fetchdomains)
In ETRN or ODMR mode, this option specifies the list of domains
the server should ship mail for once the connection is turned
around. The default is the FQDN of the machine running fetch-
mail.
-D <domain> | --smtpaddress <domain>
(Keyword: smtpaddress)
Specify the domain to be appended to addresses in RCPT TO lines
shipped to SMTP. When this is not specified, the name of the
SMTP server (as specified by --smtphost) is used for SMTP/LMTP
and 'localhost' is used for UNIX socket/BSMTP.
--smtpname <user@domain>
(Keyword: smtpname)
Specify the domain and user to be put in RCPT TO lines shipped
to SMTP. The default user is the current local user.
-Z <nnn> | --antispam <nnn[, nnn]...>
(Keyword: antispam)
Specifies the list of numeric SMTP errors that are to be inter-
preted as a spam-block response from the listener. A value of
-1 disables this option. For the command-line option, the list
values should be comma-separated.
-m <command> | --mda <command>
(Keyword: mda)
This option lets fetchmail use a Message or Local Delivery Agent
(MDA or LDA) directly, rather than forward via SMTP or LMTP.
To avoid losing mail, use this option only with MDAs like mail-
drop or MTAs like sendmail that exit with a nonzero status on
disk-full and other delivery errors; the nonzero status tells
fetchmail that delivery failed and prevents the message from
being deleted on the server.
If fetchmail is running as root, it sets its user id while
delivering mail through an MDA as follows: First, the FETCH-
MAILUSER, LOGNAME, and USER environment variables are checked in
this order. The value of the first variable from his list that
is defined (even if it is empty!) is looked up in the system
user database. If none of the variables is defined, fetchmail
will use the real user id it was started with. If one of the
variables was defined, but the user stated there isn't found,
fetchmail continues running as root, without checking remaining
variables on the list. Practically, this means that if you run
fetchmail as root (not recommended), it is most useful to define
the FETCHMAILUSER environment variable to set the user that the
MDA should run as. Some MDAs (such as maildrop) are designed to
be setuid root and setuid to the recipient's user id, so you
don't lose functionality this way even when running fetchmail as
unprivileged user. Check the MDA's manual for details.
Some possible MDAs are "/usr/sbin/sendmail -i -f %F -- %T"
(Note: some several older or vendor sendmail versions mistake --
for an address, rather than an indicator to mark the end of the
option arguments), "/usr/bin/deliver" and "/usr/bin/maildrop -d
%T". Local delivery addresses will be inserted into the MDA
command wherever you place a %T; the mail message's From address
will be inserted where you place an %F.
Do NOT enclose the %F or %T string in single quotes! For both
%T and %F, fetchmail encloses the addresses in single quotes
('), after removing any single quotes they may contain, before
the MDA command is passed to the shell.
Do NOT use an MDA invocation that dispatches on the contents of
To/Cc/Bcc, like "sendmail -i -t" or "qmail-inject", it will cre-
ate mail loops and bring the just wrath of many postmasters down
upon your head. This is one of the most frequent configuration
errors!
Also, do not try to combine multidrop mode with an MDA such as
maildrop that can only accept one address, unless your upstream
stores one copy of the message per recipient and transports the
envelope recipient in a header; you will lose mail.
The well-known procmail(1) package is very hard to configure
properly, it has a very nasty "fall through to the next rule"
behavior on delivery errors (even temporary ones, such as out of
disk space if another user's mail daemon copies the mailbox
around to purge old messages), so your mail will end up in the
wrong mailbox sooner or later. The proper procmail configuration
is outside the scope of this document. Using maildrop(1) is usu-
ally much easier, and many users find the filter syntax used by
maildrop easier to understand.
Finally, we strongly advise that you do not use qmail-inject.
The command line interface is non-standard without providing
benefits for typical use, and fetchmail makes no attempts to
accommodate qmail-inject's deviations from the standard. Some of
qmail-inject's command-line and environment options are actually
dangerous and can cause broken threads, non-detected duplicate
messages and forwarding loops.
--lmtp (Keyword: lmtp)
Cause delivery via LMTP (Local Mail Transfer Protocol). A ser-
vice host and port must be explicitly specified on each host in
the smtphost hunt list (see above) if this option is selected;
the default port 25 will (in accordance with RFC 2033) not be
accepted.
--bsmtp <filename>
(Keyword: bsmtp)
Append fetched mail to a BSMTP file. This simply contains the
SMTP commands that would normally be generated by fetchmail when
passing mail to an SMTP listener daemon.
An argument of '-' causes the SMTP batch to be written to stan-
dard output, which is of limited use: this only makes sense for
debugging, because fetchmail's regular output is interspersed on
the same channel, so this isn't suitable for mail delivery. This
special mode may be removed in a later release.
Note that fetchmail's reconstruction of MAIL FROM and RCPT TO
lines is not guaranteed correct; the caveats discussed under THE
USE AND ABUSE OF MULTIDROP MAILBOXES below apply. This mode has
precedence before --mda and SMTP/LMTP.
--bad-header {reject|accept}
(Keyword: bad-header; since v6.3.15)
Specify how fetchmail is supposed to treat messages with bad
headers, i. e. headers with bad syntax. Traditionally, fetchmail
has rejected such messages, but some distributors modified
fetchmail to accept them. You can now configure fetchmail's be-
haviour per server.
Resource Limit Control Options
-l <maxbytes> | --limit <maxbytes>
(Keyword: limit)
Takes a maximum octet size argument, where 0 is the default and
also the special value designating "no limit". If nonzero, mes-
sages larger than this size will not be fetched and will be left
on the server (in foreground sessions, the progress messages
will note that they are "oversized"). If the fetch protocol
permits (in particular, under IMAP or POP3 without the fetchall
option) the message will not be marked seen.
An explicit --limit of 0 overrides any limits set in your run
control file. This option is intended for those needing to
strictly control fetch time due to expensive and variable phone
rates.
Combined with --limitflush, it can be used to delete oversized
messages waiting on a server. In daemon mode, oversize notifi-
cations are mailed to the calling user (see the --warnings
option). This option does not work with ETRN or ODMR.
-w <interval> | --warnings <interval>
(Keyword: warnings)
Takes an interval in seconds. When you call fetchmail with a
'limit' option in daemon mode, this controls the interval at
which warnings about oversized messages are mailed to the call-
ing user (or the user specified by the 'postmaster' option).
One such notification is always mailed at the end of the the
first poll that the oversized message is detected. Thereafter,
re-notification is suppressed until after the warning interval
elapses (it will take place at the end of the first following
poll).
-b <count> | --batchlimit <count>
(Keyword: batchlimit)
Specify the maximum number of messages that will be shipped to
an SMTP listener before the connection is deliberately torn down
and rebuilt (defaults to 0, meaning no limit). An explicit
--batchlimit of 0 overrides any limits set in your run control
file. While sendmail(8) normally initiates delivery of a mes-
sage immediately after receiving the message terminator, some
SMTP listeners are not so prompt. MTAs like smail(8) may wait
till the delivery socket is shut down to deliver. This may pro-
duce annoying delays when fetchmail is processing very large
batches. Setting the batch limit to some nonzero size will pre-
vent these delays. This option does not work with ETRN or ODMR.
-B <number> | --fetchlimit <number>
(Keyword: fetchlimit)
Limit the number of messages accepted from a given server in a
single poll. By default there is no limit. An explicit --fetch-
limit of 0 overrides any limits set in your run control file.
This option does not work with ETRN or ODMR.
--fetchsizelimit <number>
(Keyword: fetchsizelimit)
Limit the number of sizes of messages accepted from a given
server in a single transaction. This option is useful in reduc-
ing the delay in downloading the first mail when there are too
many mails in the mailbox. By default, the limit is 100. If
set to 0, sizes of all messages are downloaded at the start.
This option does not work with ETRN or ODMR. For POP3, the only
valid non-zero value is 1.
--fastuidl <number>
(Keyword: fastuidl)
Do a binary instead of linear search for the first unseen UID.
Binary search avoids downloading the UIDs of all mails. This
saves time (especially in daemon mode) where downloading the
same set of UIDs in each poll is a waste of bandwidth. The num-
ber 'n' indicates how rarely a linear search should be done. In
daemon mode, linear search is used once followed by binary
searches in 'n-1' polls if 'n' is greater than 1; binary search
is always used if 'n' is 1; linear search is always used if 'n'
is 0. In non-daemon mode, binary search is used if 'n' is 1;
otherwise linear search is used. The default value of 'n' is 4.
This option works with POP3 only.
-e <count> | --expunge <count>
(Keyword: expunge)
Arrange for deletions to be made final after a given number of
messages. Under POP2 or POP3, fetchmail cannot make deletions
final without sending QUIT and ending the session -- with this
option on, fetchmail will break a long mail retrieval session
into multiple sub-sessions, sending QUIT after each sub-session.
This is a good defense against line drops on POP3 servers.
Under IMAP, fetchmail normally issues an EXPUNGE command after
each deletion in order to force the deletion to be done immedi-
ately. This is safest when your connection to the server is
flaky and expensive, as it avoids resending duplicate mail after
a line hit. However, on large mailboxes the overhead of re-
indexing after every message can slam the server pretty hard, so
if your connection is reliable it is good to do expunges less
frequently. Also note that some servers enforce a delay of a
few seconds after each quit, so fetchmail may not be able to get
back in immediately after an expunge -- you may see "lock busy"
errors if this happens. If you specify this option to an integer
N, it tells fetchmail to only issue expunges on every Nth
delete. An argument of zero suppresses expunges entirely (so no
expunges at all will be done until the end of run). This option
does not work with ETRN or ODMR.
Authentication Options
-u <name> | --user <name> | --username <name>
(Keyword: user[name])
Specifies the user identification to be used when logging in to
the mailserver. The appropriate user identification is both
server and user-dependent. The default is your login name on
the client machine that is running fetchmail. See USER AUTHEN-
TICATION below for a complete description.
-I <specification> | --interface <specification>
(Keyword: interface)
Require that a specific interface device be up and have a spe-
cific local or remote IPv4 (IPv6 is not supported by this option
yet) address (or range) before polling. Frequently fetchmail is
used over a transient point-to-point TCP/IP link established
directly to a mailserver via SLIP or PPP. That is a relatively
secure channel. But when other TCP/IP routes to the mailserver
exist (e.g. when the link is connected to an alternate ISP),
your username and password may be vulnerable to snooping (espe-
cially when daemon mode automatically polls for mail, shipping a
clear password over the net at predictable intervals). The
--interface option may be used to prevent this. When the speci-
fied link is not up or is not connected to a matching IP
address, polling will be skipped. The format is:
interface/iii.iii.iii.iii[/mmm.mmm.mmm.mmm]
The field before the first slash is the interface name (i.e.
sl0, ppp0 etc.). The field before the second slash is the
acceptable IP address. The field after the second slash is a
mask which specifies a range of IP addresses to accept. If no
mask is present 255.255.255.255 is assumed (i.e. an exact
match). This option is currently only supported under Linux and
FreeBSD. Please see the monitor section for below for FreeBSD
specific information.
Note that this option may be removed from a future fetchmail
version.
-M <interface> | --monitor <interface>
(Keyword: monitor)
Daemon mode can cause transient links which are automatically
taken down after a period of inactivity (e.g. PPP links) to
remain up indefinitely. This option identifies a system TCP/IP
interface to be monitored for activity. After each poll inter-
val, if the link is up but no other activity has occurred on the
link, then the poll will be skipped. However, when fetchmail is
woken up by a signal, the monitor check is skipped and the poll
goes through unconditionally. This option is currently only
supported under Linux and FreeBSD. For the monitor and inter-
face options to work for non root users under FreeBSD, the
fetchmail binary must be installed SGID kmem. This would be a
security hole, but fetchmail runs with the effective GID set to
that of the kmem group only when interface data is being col-
lected.
Note that this option may be removed from a future fetchmail
version.
--auth <type>
(Keyword: auth[enticate])
This option permits you to specify an authentication type (see
USER AUTHENTICATION below for details). The possible values are
any, password, kerberos_v5, kerberos (or, for excruciating
exactness, kerberos_v4), gssapi, cram-md5, otp, ntlm, msn (only
for POP3), external (only IMAP) and ssh. When any (the default)
is specified, fetchmail tries first methods that don't require a
password (EXTERNAL, GSSAPI, KERBEROS IV, KERBEROS 5); then it
looks for methods that mask your password (CRAM-MD5, NTLM, X-OTP
- note that MSN is only supported for POP3, but not autoprobed);
and only if the server doesn't support any of those will it ship
your password en clair. Other values may be used to force vari-
ous authentication methods (ssh suppresses authentication and is
thus useful for IMAP PREAUTH). (external suppresses authentica-
tion and is thus useful for IMAP EXTERNAL). Any value other
than password, cram-md5, ntlm, msn or otp suppresses fetchmail's
normal inquiry for a password. Specify ssh when you are using
an end-to-end secure connection such as an ssh tunnel; specify
external when you use TLS with client authentication and specify
gssapi or kerberos_v4 if you are using a protocol variant that
employs GSSAPI or K4. Choosing KPOP protocol automatically
selects Kerberos authentication. This option does not work with
ETRN. GSSAPI service names are in line with RFC-2743 and IANA
registrations, see Generic Security Service Application Program
Interface (GSSAPI)/Kerberos/Simple Authentication and Security
Layer (SASL) Service Names <http://www.iana.org/assignments/
gssapi-service-names/>.
Miscellaneous Options
-f <pathname> | --fetchmailrc <pathname>
Specify a non-default name for the ~/.fetchmailrc run control
file. The pathname argument must be either "-" (a single dash,
meaning to read the configuration from standard input) or a
filename. Unless the --version option is also on, a named file
argument must have permissions no more open than 0700
(u=rwx,g=,o=) or else be /dev/null.
-i <pathname> | --idfile <pathname>
(Keyword: idfile)
Specify an alternate name for the .fetchids file used to save
message UIDs. NOTE: since fetchmail 6.3.0, write access to the
directory containing the idfile is required, as fetchmail writes
a temporary file and renames it into the place of the real
idfile only if the temporary file has been written successfully.
This avoids the truncation of idfiles when running out of disk
space.
--pidfile <pathname>
(Keyword: pidfile; since fetchmail v6.3.4)
Override the default location of the PID file. Default: see
"ENVIRONMENT" below.
-n | --norewrite
(Keyword: no rewrite)
Normally, fetchmail edits RFC-822 address headers (To, From, Cc,
Bcc, and Reply-To) in fetched mail so that any mail IDs local to
the server are expanded to full addresses (@ and the mailserver
hostname are appended). This enables replies on the client to
get addressed correctly (otherwise your mailer might think they
should be addressed to local users on the client machine!).
This option disables the rewrite. (This option is provided to
pacify people who are paranoid about having an MTA edit mail
headers and want to know they can prevent it, but it is gener-
ally not a good idea to actually turn off rewrite.) When using
ETRN or ODMR, the rewrite option is ineffective.
-E <line> | --envelope <line>
(Keyword: envelope; Multidrop only)
In the configuration file, an enhanced syntax is used:
envelope [<count>] <line>
This option changes the header fetchmail assumes will carry a
copy of the mail's envelope address. Normally this is 'X-Enve-
lope-To'. Other typically found headers to carry envelope
information are 'X-Original-To' and 'Delivered-To'. Now, since
these headers are not standardized, practice varies. See the
discussion of multidrop address handling below. As a special
case, 'envelope "Received"' enables parsing of sendmail-style
Received lines. This is the default, but discouraged because it
is not fully reliable.
Note that fetchmail expects the Received-line to be in a spe-
cific format: It must contain "by host for address", where host
must match one of the mailserver names that fetchmail recognizes
for the account in question.
The optional count argument (only available in the configuration
file) determines how many header lines of this kind are skipped.
A count of 1 means: skip the first, take the second. A count of
2 means: skip the first and second, take the third, and so on.
-Q <prefix> | --qvirtual <prefix>
(Keyword: qvirtual; Multidrop only)
The string prefix assigned to this option will be removed from
the user name found in the header specified with the envelope
option (before doing multidrop name mapping or localdomain
checking, if either is applicable). This option is useful if you
are using fetchmail to collect the mail for an entire domain and
your ISP (or your mail redirection provider) is using qmail.
One of the basic features of qmail is the Delivered-To: message
header. Whenever qmail delivers a message to a local mailbox it
puts the username and hostname of the envelope recipient on this
line. The major reason for this is to prevent mail loops. To
set up qmail to batch mail for a disconnected site the ISP-mail-
host will have normally put that site in its 'Virtualhosts' con-
trol file so it will add a prefix to all mail addresses for this
site. This results in mail sent to 'username AT userhost.user-
dom.dom.com' having a Delivered-To: line of the form:
Delivered-To: mbox-userstr-username AT userhost.com
The ISP can make the 'mbox-userstr-' prefix anything they choose
but a string matching the user host name is likely. By using
the option 'envelope Delivered-To:' you can make fetchmail reli-
ably identify the original envelope recipient, but you have to
strip the 'mbox-userstr-' prefix to deliver to the correct user.
This is what this option is for.
--configdump
Parse the ~/.fetchmailrc file, interpret any command-line
options specified, and dump a configuration report to standard
output. The configuration report is a data structure assignment
in the language Python. This option is meant to be used with an
interactive ~/.fetchmailrc editor like fetchmailconf, written in
Python.
-y | --yydebug
Enables parser debugging, this option is meant to be used by
developers only.
Removed Options
-T | --netsec
Removed before version 6.3.0, the required underlying inet6_apps
library had been discontinued and is no longer available.
USER AUTHENTICATION AND ENCRYPTION
All modes except ETRN require authentication of the client to the
server. Normal user authentication in fetchmail is very much like the
authentication mechanism of ftp(1). The correct user-id and password
depend upon the underlying security system at the mailserver.
If the mailserver is a Unix machine on which you have an ordinary user
account, your regular login name and password are used with fetchmail.
If you use the same login name on both the server and the client
machines, you needn't worry about specifying a user-id with the -u
option -- the default behavior is to use your login name on the client
machine as the user-id on the server machine. If you use a different
login name on the server machine, specify that login name with the -u
option. e.g. if your login name is 'jsmith' on a machine named 'mail-
grunt', you would start fetchmail as follows:
fetchmail -u jsmith mailgrunt
The default behavior of fetchmail is to prompt you for your mailserver
password before the connection is established. This is the safest way
to use fetchmail and ensures that your password will not be compro-
mised. You may also specify your password in your ~/.fetchmailrc file.
This is convenient when using fetchmail in daemon mode or with scripts.
Using netrc files
If you do not specify a password, and fetchmail cannot extract one from
your ~/.fetchmailrc file, it will look for a ~/.netrc file in your home
directory before requesting one interactively; if an entry matching the
mailserver is found in that file, the password will be used. Fetchmail
first looks for a match on poll name; if it finds none, it checks for a
match on via name. See the ftp(1) man page for details of the syntax
of the ~/.netrc file. To show a practical example, a .netrc might look
like this:
machine hermes.example.org
login joe
password topsecret
You can repeat this block with different user information if you need
to provide more than one password.
This feature may allow you to avoid duplicating password information in
more than one file.
On mailservers that do not provide ordinary user accounts, your user-id
and password are usually assigned by the server administrator when you
apply for a mailbox on the server. Contact your server administrator
if you don't know the correct user-id and password for your mailbox
account.
POP3 VARIANTS
Early versions of POP3 (RFC1081, RFC1225) supported a crude form of
independent authentication using the .rhosts file on the mailserver
side. Under this RPOP variant, a fixed per-user ID equivalent to a
password was sent in clear over a link to a reserved port, with the
command RPOP rather than PASS to alert the server that it should do
special checking. RPOP is supported by fetchmail (you can specify
'protocol RPOP' to have the program send 'RPOP' rather than 'PASS') but
its use is strongly discouraged, and support will be removed from a
future fetchmail version. This facility was vulnerable to spoofing and
was withdrawn in RFC1460.
RFC1460 introduced APOP authentication. In this variant of POP3, you
register an APOP password on your server host (on some servers, the
program to do this is called popauth(8)). You put the same password in
your ~/.fetchmailrc file. Each time fetchmail logs in, it sends an MD5
hash of your password and the server greeting time to the server, which
can verify it by checking its authorization database.
Note that APOP is no longer considered resistant against man-in-the-
middle attacks.
RETR or TOP
fetchmail makes some efforts to make the server believe messages had
not been retrieved, by using the TOP command with a large number of
lines when possible. TOP is a command that retrieves the full header
and a fetchmail-specified amount of body lines. It is optional and
therefore not implemented by all servers, and some are known to imple-
ment it improperly. On many servers however, the RETR command which
retrieves the full message with header and body, sets the "seen" flag
(for instance, in a web interface), whereas the TOP command does not do
that.
fetchmail will always use the RETR command if "fetchall" is set.
fetchmail will also use the RETR command if "keep" is set and "uidl" is
unset. Finally, fetchmail will use the RETR command on Maillennium
POP3/PROXY servers (used by Comcast) to avoid a deliberate TOP misin-
terpretation in this server that causes message corruption.
In all other cases, fetchmail will use the TOP command. This implies
that in "keep" setups, "uidl" must be set if "TOP" is desired.
Note that this description is true for the current version of fetch-
mail, but the behavior may change in future versions. In particular,
fetchmail may prefer the RETR command because the TOP command causes
much grief on some servers and is only optional.
ALTERNATE AUTHENTICATION FORMS
If your fetchmail was built with Kerberos support and you specify Ker-
beros authentication (either with --auth or the .fetchmailrc option
authenticate kerberos_v4) it will try to get a Kerberos ticket from the
mailserver at the start of each query. Note: if either the pollname or
via name is 'hesiod', fetchmail will try to use Hesiod to look up the
mailserver.
If you use POP3 or IMAP with GSSAPI authentication, fetchmail will
expect the server to have RFC1731- or RFC1734-conforming GSSAPI capa-
bility, and will use it. Currently this has only been tested over Ker-
beros V, so you're expected to already have a ticket-granting ticket.
You may pass a username different from your principal name using the
standard --user command or by the .fetchmailrc option user.
If your IMAP daemon returns the PREAUTH response in its greeting line,
fetchmail will notice this and skip the normal authentication step.
This can be useful, e.g. if you start imapd explicitly using ssh. In
this case you can declare the authentication value 'ssh' on that site
entry to stop .fetchmail from asking you for a password when it starts
up.
If you use client authentication with TLS1 and your IMAP daemon returns
the AUTH=EXTERNAL response, fetchmail will notice this and will use the
authentication shortcut and will not send the passphrase. In this case
you can declare the authentication value 'external'
on that site to stop fetchmail from asking you for a password when it
starts up.
If you are using POP3, and the server issues a one-time-password chal-
lenge conforming to RFC1938, fetchmail will use your password as a pass
phrase to generate the required response. This avoids sending secrets
over the net unencrypted.
Compuserve's RPA authentication is supported. If you compile in the
support, fetchmail will try to perform an RPA pass-phrase authentica-
tion instead of sending over the password en clair if it detects "@com-
puserve.com" in the hostname.
If you are using IMAP, Microsoft's NTLM authentication (used by Micro-
soft Exchange) is supported. If you compile in the support, fetchmail
will try to perform an NTLM authentication (instead of sending over the
password en clair) whenever the server returns AUTH=NTLM in its capa-
bility response. Specify a user option value that looks like
'user@domain': the part to the left of the @ will be passed as the
username and the part to the right as the NTLM domain.
Secure Socket Layers (SSL) and Transport Layer Security (TLS)
transport. Additionally, POP3 and IMAP retrival can also negotiate
SSL/TLS by means of STARTTLS (or STLS).
Note that fetchmail currently uses the OpenSSL library, which is se-
verely underdocumented, so failures may occur just because the program-
mers are not aware of OpenSSL's requirement of the day. For instance,
since v6.3.16, fetchmail calls OpenSSL_add_all_algorithms(), which is
necessary to support certificates using SHA256 on OpenSSL 0.9.8 -- this
information is deeply hidden in the documentation and not at all obvi-
ous. Please do not hesitate to report subtle SSL failures.
You can access SSL encrypted services by specifying the options start-
ing with --ssl, such as --ssl, --sslproto, --sslcertck, and others.
You can also do this using the corresponding user options in the
.fetchmailrc file. Some services, such as POP3 and IMAP, have differ-
ent well known ports defined for the SSL encrypted services. The
encrypted ports will be selected automatically when SSL is enabled and
no explicit port is specified. Also, the --sslcertck command line or
sslcertck run control file option should be used to force strict cer-
tificate checking - see below.
If SSL is not configured, fetchmail will usually opportunistically try
to use STARTTLS. STARTTLS can be enforced by using --sslproto auto and
defeated by using --sslproto ''. TLS connections use the same port as
the unencrypted version of the protocol and negotiate TLS via special
command. The --sslcertck command line or sslcertck run control file
option should be used to force strict certificate checking - see below.
--sslcertck is recommended: When connecting to an SSL or TLS encrypted
server, the server presents a certificate to the client for validation.
The certificate is checked to verify that the common name in the cer-
tificate matches the name of the server being contacted and that the
effective and expiration dates in the certificate indicate that it is
currently valid. If any of these checks fail, a warning message is
printed, but the connection continues. The server certificate does not
need to be signed by any specific Certifying Authority and may be a
"self-signed" certificate. If the --sslcertck command line option or
sslcertck run control file option is used, fetchmail will instead abort
if any of these checks fail, because it must assume that there is a
man-in-the-middle attack in this scenario, hence fetchmail must not
expose cleartext passwords. Use of the sslcertck or --sslcertck option
is therefore advised.
Some SSL encrypted servers may request a client side certificate. A
client side public SSL certificate and private SSL key may be speci-
fied. If requested by the server, the client certificate is sent to
the server for validation. Some servers may require a valid client
certificate and may refuse connections if a certificate is not provided
or if the certificate is not valid. Some servers may require client
side certificates be signed by a recognized Certifying Authority. The
format for the key files and the certificate files is that required by
the underlying SSL libraries (OpenSSL in the general case).
A word of care about the use of SSL: While above mentioned setup with
self-signed server certificates retrieved over the wires can protect
you from a passive eavesdropper, it doesn't help against an active
attacker. It's clearly an improvement over sending the passwords in
clear, but you should be aware that a man-in-the-middle attack is triv-
ially possible (in particular with tools such as dsniff <http://
monkey.org/~dugsong/dsniff/>, ). Use of strict certificate checking
with a certification authority recognized by server and client, or per-
haps of an SSH tunnel (see below for some examples) is preferable if
you care seriously about the security of your mailbox and passwords.
ESMTP AUTH
fetchmail also supports authentication to the ESMTP server on the
client side according to RFC 2554. You can specify a name/password
pair to be used with the keywords 'esmtpname' and 'esmtppassword'; the
former defaults to the username of the calling user.
DAEMON MODE
Introducing the daemon mode
In daemon mode, fetchmail puts itself into the background and runs for-
ever, querying each specified host and then sleeping for a given
polling interval.
Starting the daemon mode
There are several ways to make fetchmail work in daemon mode. On the
command line, --daemon <interval> or -d <interval> option runs fetch-
mail in daemon mode. You must specify a numeric argument which is a
polling interval (time to wait after completing a whole poll cycle with
the last server and before starting the next poll cycle with the first
server) in seconds.
Example: simply invoking
fetchmail -d 900
will, therefore, poll all the hosts described in your ~/.fetchmailrc
file (except those explicitly excluded with the 'skip' verb) a bit less
often than once every 15 minutes (exactly: 15 minutes + time that the
poll takes).
It is also possible to set a polling interval in your ~/.fetchmailrc
file by saying 'set daemon <interval>', where <interval> is an integer
number of seconds. If you do this, fetchmail will always start in dae-
mon mode unless you override it with the command-line option --daemon 0
or -d0.
Only one daemon process is permitted per user; in daemon mode, fetch-
mail sets up a per-user lockfile to guarantee this. (You can however
cheat and set the FETCHMAILHOME environment variable to overcome this
setting, but in that case, it is your responsibility to make sure you
aren't polling the same server with two processes at the same time.)
Awakening the background daemon
Normally, calling fetchmail with a daemon in the background sends a
wake-up signal to the daemon and quits without output. The background
daemon then starts its next poll cycle immediately. The wake-up sig-
nal, SIGUSR1, can also be sent manually. The wake-up action also clears
any 'wedged' flags indicating that connections have wedged due to
failed authentication or multiple timeouts.
Terminating the background daemon
The option -q or --quit will kill a running daemon process instead of
waking it up (if there is no such process, fetchmail will notify you).
If the --quit option appears last on the command line, fetchmail will
kill the running daemon process and then quit. Otherwise, fetchmail
will first kill a running daemon process and then continue running with
the other options.
Useful options for daemon mode
The -L <filename> or --logfile <filename> option (keyword: set logfile)
is only effective when fetchmail is detached and in daemon mode. Note
that the logfile must exist before fetchmail is run, you can use the
touch(1) command with the filename as its sole argument to create it.
This option allows you to redirect status messages into a specified
logfile (follow the option with the logfile name). The logfile is
opened for append, so previous messages aren't deleted. This is pri-
marily useful for debugging configurations. Note that fetchmail does
not detect if the logfile is rotated, the logfile is only opened once
when fetchmail starts. You need to restart fetchmail after rotating the
logfile and before compressing it (if applicable).
The --syslog option (keyword: set syslog) allows you to redirect status
and error messages emitted to the syslog(3) system daemon if available.
Messages are logged with an id of fetchmail, the facility LOG_MAIL, and
priorities LOG_ERR, LOG_ALERT or LOG_INFO. This option is intended for
logging status and error messages which indicate the status of the dae-
mon and the results while fetching mail from the server(s). Error mes-
sages for command line options and parsing the .fetchmailrc file are
still written to stderr, or to the specified log file. The --nosyslog
option turns off use of syslog(3), assuming it's turned on in the
~/.fetchmailrc file. This option is overridden, in certain situations,
by --logfile (which see).
The -N or --nodetach option suppresses backgrounding and detachment of
the daemon process from its control terminal. This is useful for
debugging or when fetchmail runs as the child of a supervisor process
such as init(8) or Gerrit Pape's runit(8). Note that this also causes
the logfile option to be ignored.
Note that while running in daemon mode polling a POP2 or IMAP2bis
server, transient errors (such as DNS failures or sendmail delivery
refusals) may force the fetchall option on for the duration of the next
polling cycle. This is a robustness feature. It means that if a mes-
sage is fetched (and thus marked seen by the mailserver) but not deliv-
ered locally due to some transient error, it will be re-fetched during
the next poll cycle. (The IMAP logic doesn't delete messages until
they're delivered, so this problem does not arise.)
If you touch or change the ~/.fetchmailrc file while fetchmail is run-
ning in daemon mode, this will be detected at the beginning of the next
poll cycle. When a changed ~/.fetchmailrc is detected, fetchmail
rereads it and restarts from scratch (using exec(2); no state informa-
tion is retained in the new instance). Note that if fetchmail needs to
query for passwords, of that if you break the ~/.fetchmailrc file's
syntax, the new instance will softly and silently vanish away on
startup.
ADMINISTRATIVE OPTIONS
The --postmaster <name> option (keyword: set postmaster) specifies the
last-resort username to which multidrop mail is to be forwarded if no
matching local recipient can be found. It is also used as destination
of undeliverable mail if the 'bouncemail' global option is off and
additionally for spam-blocked mail if the 'bouncemail' global option is
off and the 'spambounce' global option is on. This option defaults to
the user who invoked fetchmail. If the invoking user is root, then the
default of this option is the user 'postmaster'. Setting postmaster to
the empty string causes such mail as described above to be discarded -
this however is usually a bad idea. See also the description of the
'FETCHMAILUSER' environment variable in the ENVIRONMENT section below.
The --nobounce behaves like the "set no bouncemail" global option,
which see.
The --invisible option (keyword: set invisible) tries to make fetchmail
invisible. Normally, fetchmail behaves like any other MTA would -- it
generates a Received header into each message describing its place in
the chain of transmission, and tells the MTA it forwards to that the
mail came from the machine fetchmail itself is running on. If the
invisible option is on, the Received header is suppressed and fetchmail
tries to spoof the MTA it forwards to into thinking it came directly
from the mailserver host.
The --showdots option (keyword: set showdots) forces fetchmail to show
progress dots even if the output goes to a file or fetchmail is not in
verbose mode. Fetchmail shows the dots by default when run in --ver-
bose mode and output goes to console. This option is ignored in
--silent mode.
By specifying the --tracepolls option, you can ask fetchmail to add
information to the Received header on the form "polling {label} account
{user}", where {label} is the account label (from the specified rcfile,
normally ~/.fetchmailrc) and {user} is the username which is used to
log on to the mail server. This header can be used to make filtering
email where no useful header information is available and you want mail
from different accounts sorted into different mailboxes (this could,
for example, occur if you have an account on the same server running a
mailing list, and are subscribed to the list using that account). The
default is not adding any such header. In .fetchmailrc, this is called
'tracepolls'.
RETRIEVAL FAILURE MODES
The protocols fetchmail uses to talk to mailservers are next to bullet-
proof. In normal operation forwarding to port 25, no message is ever
deleted (or even marked for deletion) on the host until the SMTP lis-
tener on the client side has acknowledged to fetchmail that the message
has been either accepted for delivery or rejected due to a spam block.
When forwarding to an MDA, however, there is more possibility of error.
Some MDAs are 'safe' and reliably return a nonzero status on any deliv-
ery error, even one due to temporary resource limits. The maildrop(1)
program is like this; so are most programs designed as mail transport
agents, such as sendmail(1), including the sendmail wrapper of Postfix
and exim(1). These programs give back a reliable positive acknowledge-
ment and can be used with the mda option with no risk of mail loss.
Unsafe MDAs, though, may return 0 even on delivery failure. If this
happens, you will lose mail.
The normal mode of fetchmail is to try to download only 'new' messages,
leaving untouched (and undeleted) messages you have already read
directly on the server (or fetched with a previous fetchmail --keep).
But you may find that messages you've already read on the server are
being fetched (and deleted) even when you don't specify --all. There
are several reasons this can happen.
One could be that you're using POP2. The POP2 protocol includes no
representation of 'new' or 'old' state in messages, so fetchmail must
treat all messages as new all the time. But POP2 is obsolete, so this
is unlikely.
A potential POP3 problem might be servers that insert messages in the
middle of mailboxes (some VMS implementations of mail are rumored to do
this). The fetchmail code assumes that new messages are appended to
the end of the mailbox; when this is not true it may treat some old
messages as new and vice versa. Using UIDL whilst setting fastuidl 0
might fix this, otherwise, consider switching to IMAP.
Yet another POP3 problem is that if they can't make tempfiles in the
user's home directory, some POP3 servers will hand back an undocumented
response that causes fetchmail to spuriously report "No mail".
The IMAP code uses the presence or absence of the server flag \Seen to
decide whether or not a message is new. This isn't the right thing to
do, fetchmail should check the UIDVALIDITY and use UID, but it doesn't
do that yet. Under Unix, it counts on your IMAP server to notice the
BSD-style Status flags set by mail user agents and set the \Seen flag
from them when appropriate. All Unix IMAP servers we know of do this,
though it's not specified by the IMAP RFCs. If you ever trip over a
server that doesn't, the symptom will be that messages you have already
read on your host will look new to the server. In this (unlikely)
case, only messages you fetched with fetchmail --keep will be both
undeleted and marked old.
In ETRN and ODMR modes, fetchmail does not actually retrieve messages;
instead, it asks the server's SMTP listener to start a queue flush to
the client via SMTP. Therefore it sends only undelivered messages.
SPAM FILTERING
Many SMTP listeners allow administrators to set up 'spam filters' that
block unsolicited email from specified domains. A MAIL FROM or DATA
line that triggers this feature will elicit an SMTP response which
(unfortunately) varies according to the listener.
Newer versions of sendmail return an error code of 571.
According to RFC2821, the correct thing to return in this situation is
550 "Requested action not taken: mailbox unavailable" (the draft adds
"[E.g., mailbox not found, no access, or command rejected for policy
reasons].").
Older versions of the exim MTA return 501 "Syntax error in parameters
or arguments".
The postfix MTA runs 554 as an antispam response.
Zmailer may reject code with a 500 response (followed by an enhanced
status code that contains more information).
Return codes which fetchmail treats as antispam responses and discards
the message can be set with the 'antispam' option. This is one of the
only three circumstance under which fetchmail ever discards mail (the
others are the 552 and 553 errors described below, and the suppression
of multidropped messages with a message-ID already seen).
If fetchmail is fetching from an IMAP server, the antispam response
will be detected and the message rejected immediately after the headers
have been fetched, without reading the message body. Thus, you won't
pay for downloading spam message bodies.
By default, the list of antispam responses is empty.
If the spambounce global option is on, mail that is spam-blocked trig-
gers an RFC1892/RFC1894 bounce message informing the originator that we
do not accept mail from it. See also BUGS.
SMTP/ESMTP ERROR HANDLING
Besides the spam-blocking described above, fetchmail takes special
actions on the following SMTP/ESMTP error responses
452 (insufficient system storage)
Leave the message in the server mailbox for later retrieval.
552 (message exceeds fixed maximum message size)
Delete the message from the server. Send bounce-mail to the orig-
inator.
553 (invalid sending domain)
Delete the message from the server. Don't even try to send
bounce-mail to the originator.
Other errors trigger bounce mail back to the originator. See also BUGS.
THE RUN CONTROL FILE
The preferred way to set up fetchmail is to write a .fetchmailrc file
in your home directory (you may do this directly, with a text editor,
or indirectly via fetchmailconf). When there is a conflict between the
command-line arguments and the arguments in this file, the command-line
arguments take precedence.
To protect the security of your passwords, your ~/.fetchmailrc may not
normally have more than 0700 (u=rwx,g=,o=) permissions; fetchmail will
complain and exit otherwise (this check is suppressed when --version is
on).
You may read the .fetchmailrc file as a list of commands to be executed
when fetchmail is called with no arguments.
Run Control Syntax
Comments begin with a '#' and extend through the end of the line. Oth-
erwise the file consists of a series of server entries or global option
statements in a free-format, token-oriented syntax.
There are four kinds of tokens: grammar keywords, numbers (i.e. decimal
digit sequences), unquoted strings, and quoted strings. A quoted
string is bounded by double quotes and may contain whitespace (and
quoted digits are treated as a string). Note that quoted strings will
also contain line feed characters if they run across two or more lines,
unless you use a backslash to join lines (see below). An unquoted
string is any whitespace-delimited token that is neither numeric,
string quoted nor contains the special characters ',', ';', ':', or
'='.
Any amount of whitespace separates tokens in server entries, but is
otherwise ignored. You may use backslash escape sequences (\n for LF,
\t for HT, \b for BS, \r for CR, \nnn for decimal (where nnn cannot
start with a 0), \0ooo for octal, and \xhh for hex) to embed non-print-
able characters or string delimiters in strings. In quoted strings, a
backslash at the very end of a line will cause the backslash itself and
the line feed (LF or NL, new line) character to be ignored, so that you
can wrap long strings. Without the backslash at the line end, the line
feed character would become part of the string.
Warning: while these resemble C-style escape sequences, they are not
the same. fetchmail only supports these eight styles. C supports more
escape sequences that consist of backslash (\) and a single character,
but does not support decimal codes and does not require the leading 0
in octal notation. Example: fetchmail interprets \233 the same as \xE9
(Latin small letter e with acute), where C would interpret \233 as
octal 0233 = \x9B (CSI, control sequence introducer).
Each server entry consists of one of the keywords 'poll' or 'skip',
followed by a server name, followed by server options, followed by any
number of user (or username) descriptions, followed by user options.
Note: the most common cause of syntax errors is mixing up user and
server options or putting user options before the user descriptions.
For backward compatibility, the word 'server' is a synonym for 'poll'.
You can use the noise keywords 'and', 'with', 'has', 'wants', and
'options' anywhere in an entry to make it resemble English. They're
ignored, but but can make entries much easier to read at a glance. The
punctuation characters ':', ';' and ',' are also ignored.
Poll vs. Skip
The 'poll' verb tells fetchmail to query this host when it is run with
no arguments. The 'skip' verb tells fetchmail not to poll this host
unless it is explicitly named on the command line. (The 'skip' verb
allows you to experiment with test entries safely, or easily disable
entries for hosts that are temporarily down.)
Keyword/Option Summary
Here are the legal options. Keyword suffixes enclosed in square brack-
ets are optional. Those corresponding to short command-line options
are followed by '-' and the appropriate option letter. If option is
only relevant to a single mode of operation, it is noted as 's' or 'm'
for singledrop- or multidrop-mode, respectively.
Here are the legal global options:
Keyword Opt Mode Function
--------------------------------------------------------------------
set daemon -d Set a background poll interval in
seconds.
set postmaster Give the name of the last-resort
mail recipient (default: user run-
ning fetchmail, "postmaster" if
run by the root user)
set bouncemail Direct error mail to the sender
(default)
set no bouncemail Direct error mail to the local
postmaster (as per the 'postmas-
ter' global option above).
set no spambounce Do not bounce spam-blocked mail
(default).
set spambounce Bounce blocked spam-blocked mail
(as per the 'antispam' user
option) back to the destination as
indicated by the 'bouncemail'
global option. Warning: Do not
use this to bounce spam back to
the sender - most spam is sent
with false sender address and thus
this option hurts innocent
bystanders.
set no softbounce Delete permanently undeliverable
mail. It is recommended to use
this option if the configuration
has been thoroughly tested.
set softbounce Keep permanently undeliverable
mail as though a temporary error
had occurred (default).
set logfile -L Name of a file to append error and
status messages to. Only effec-
tive in daemon mode and if fetch-
mail detaches. If effective,
overrides set syslog.
set idfile -i Name of the file to store UID
lists in.
set syslog Do error logging through sys-
log(3). May be overriden by set
logfile.
set no syslog Turn off error logging through
syslog(3). (default)
set properties String value that is ignored by
fetchmail (may be used by exten-
sion scripts).
Here are the legal server options:
Keyword Opt Mode Function
-----------------------------------------------------------------
via Specify DNS name of mailserver,
overriding poll name
proto[col] -p Specify protocol (case insensi-
tive): POP2, POP3, IMAP, APOP,
KPOP
local[domains] m Specify domain(s) to be regarded
as local
port Specify TCP/IP service port (obso-
lete, use 'service' instead).
service -P Specify service name (a numeric
value is also allowed and consid-
ered a TCP/IP port number).
auth[enticate] Set authentication type (default
'any')
timeout -t Server inactivity timeout in sec-
onds (default 300)
envelope -E m Specify envelope-address header
name
no envelope m Disable looking for envelope
address
qvirtual -Q m Qmail virtual domain prefix to
remove from user name
aka m Specify alternate DNS names of
mailserver
interface -I specify IP interface(s) that must
be up for server poll to take
place
monitor -M Specify IP address to monitor for
activity
plugin Specify command through which to
make server connections.
plugout Specify command through which to
make listener connections.
dns m Enable DNS lookup for multidrop
(default)
no dns m Disable DNS lookup for multidrop
checkalias m Do comparison by IP address for
multidrop
no checkalias m Do comparison by name for mul-
tidrop (default)
uidl -U Force POP3 to use client-side
UIDLs (recommended)
no uidl Turn off POP3 use of client-side
UIDLs (default)
interval Only check this site every N poll
cycles; N is a numeric argument.
tracepolls Add poll tracing information to
the Received header
principal Set Kerberos principal (only use-
ful with IMAP and kerberos)
esmtpname Set name for RFC2554 authentica-
tion to the ESMTP server.
esmtppassword Set password for RFC2554 authenti-
cation to the ESMTP server.
bad-header How to treat messages with a bad
header. Can be reject (default) or
accept.
Here are the legal user descriptions and options:
Keyword Opt Mode Function
-------------------------------------------------------------------
user[name] -u This is the user description and
must come first after server
description and after possible
server options, and before user
options.
It sets the remote user name if by
itself or followed by 'there', or
the local user name if followed by
'here'.
is Connect local and remote user
names
to Connect local and remote user
names
pass[word] Specify remote account password
ssl Connect to server over the speci-
fied base protocol using SSL
encryption
sslcert Specify file for client side pub-
lic SSL certificate
sslcertfile Specify file with trusted CA cer-
tificates
sslcertpath Specify c_rehash-ed directory with
trusted CA certificates.
sslkey Specify file for client side pri-
vate SSL key
sslproto Force ssl protocol for connection
folder -r Specify remote folder to query
smtphost -S Specify smtp host(s) to forward to
fetchdomains m Specify domains for which mail
should be fetched
smtpaddress -D Specify the domain to be put in
RCPT TO lines
smtpname Specify the user and domain to be
put in RCPT TO lines
antispam -Z Specify what SMTP returns are
interpreted as spam-policy blocks
mda -m Specify MDA for local delivery
bsmtp Specify BSMTP batch file to append
to
preconnect Command to be executed before each
connection
postconnect Command to be executed after each
connection
keep -k Don't delete seen messages from
server (for POP3, uidl is recom-
mended)
flush -F Flush all seen messages before
querying (DANGEROUS)
limitflush Flush all oversized messages
before querying
fetchall -a Fetch all messages whether seen or
not
rewrite Rewrite destination addresses for
reply (default)
stripcr Strip carriage returns from ends
of lines
forcecr Force carriage returns at ends of
lines
pass8bits Force BODY=8BITMIME to ESMTP lis-
tener
dropstatus Strip Status and X-Mozilla-Status
lines out of incoming mail
dropdelivered Strip Delivered-To lines out of
incoming mail
mimedecode Convert quoted-printable to 8-bit
in MIME messages
idle Idle waiting for new messages
after each poll (IMAP only)
no keep -K Delete seen messages from server
(default)
no flush Don't flush all seen messages
before querying (default)
no fetchall Retrieve only new messages
(default)
no rewrite Don't rewrite headers
no stripcr Don't strip carriage returns
(default)
no forcecr Don't force carriage returns at
EOL (default)
no pass8bits Don't force BODY=8BITMIME to ESMTP
listener (default)
no dropstatus Don't drop Status headers
(default)
no dropdelivered Don't drop Delivered-To headers
(default)
no mimedecode Don't convert quoted-printable to
8-bit in MIME messages (default)
no idle Don't idle waiting for new mes-
sages after each poll (IMAP only)
limit -l Set message size limit
warnings -w Set message size warning interval
batchlimit -b Max # messages to forward in sin-
gle connect
fetchlimit -B Max # messages to fetch in single
connect
fetchsizelimit Max # message sizes to fetch in
single transaction
fastuidl Use binary search for first unseen
message (POP3 only)
expunge -e Perform an expunge on every #th
message (IMAP and POP3 only)
properties String value is ignored by fetch-
mail (may be used by extension
scripts)
All user options must begin with a user description (user or username
option) and follow all server descriptions and options.
In the .fetchmailrc file, the 'envelope' string argument may be pre-
ceded by a whitespace-separated number. This number, if specified, is
the number of such headers to skip over (that is, an argument of 1
selects the second header of the given type). This is sometime useful
for ignoring bogus envelope headers created by an ISP's local delivery
agent or internal forwards (through mail inspection systems, for
instance).
Keywords Not Corresponding To Option Switches
The 'folder' and 'smtphost' options (unlike their command-line equiva-
lents) can take a space- or comma-separated list of names following
them.
All options correspond to the obvious command-line arguments, except
the following: 'via', 'interval', 'aka', 'is', 'to', 'dns'/'no dns',
'checkalias'/'no checkalias', 'password', 'preconnect', 'postconnect',
'localdomains', 'stripcr'/'no stripcr', 'forcecr'/'no forcecr',
'pass8bits'/'no pass8bits' 'dropstatus/no dropstatus', 'dropdeliv-
ered/no dropdelivered', 'mimedecode/no mimedecode', 'no idle', and 'no
envelope'.
The 'via' option is for if you want to have more than one configuration
pointing at the same site. If it is present, the string argument will
be taken as the actual DNS name of the mailserver host to query. This
will override the argument of poll, which can then simply be a distinct
label for the configuration (e.g. what you would give on the command
line to explicitly query this host).
The 'interval' option (which takes a numeric argument) allows you to
poll a server less frequently than the basic poll interval. If you say
'interval N' the server this option is attached to will only be queried
every N poll intervals.
Singledrop vs. Multidrop options
Please ensure you read the section titled THE USE AND ABUSE OF MUL-
TIDROP MAILBOXES if you intend to use multidrop mode.
The 'is' or 'to' keywords associate the following local (client)
name(s) (or server-name to client-name mappings separated by =) with
the mailserver user name in the entry. If an is/to list has '*' as its
last name, unrecognized names are simply passed through. Note that
until fetchmail version 6.3.4 inclusively, these lists could only con-
tain local parts of user names (fetchmail would only look at the part
before the @ sign). fetchmail versions 6.3.5 and newer support full
addresses on the left hand side of these mappings, and they take prece-
dence over any 'localdomains', 'aka', 'via' or similar mappings.
A single local name can be used to support redirecting your mail when
your username on the client machine is different from your name on the
mailserver. When there is only a single local name, mail is forwarded
to that local username regardless of the message's Received, To, Cc,
and Bcc headers. In this case, fetchmail never does DNS lookups.
When there is more than one local name (or name mapping), fetchmail
looks at the envelope header, if configured, and otherwise at the
Received, To, Cc, and Bcc headers of retrieved mail (this is 'multidrop
mode'). It looks for addresses with hostname parts that match your
poll name or your 'via', 'aka' or 'localdomains' options, and usually
also for hostname parts which DNS tells it are aliases of the
mailserver. See the discussion of 'dns', 'checkalias', 'localdomains',
and 'aka' for details on how matching addresses are handled.
If fetchmail cannot match any mailserver usernames or localdomain
addresses, the mail will be bounced. Normally it will be bounced to
the sender, but if the 'bouncemail' global option is off, the mail will
go to the local postmaster instead. (see the 'postmaster' global
option). See also BUGS.
The 'dns' option (normally on) controls the way addresses from mul-
tidrop mailboxes are checked. On, it enables logic to check each host
address that does not match an 'aka' or 'localdomains' declaration by
looking it up with DNS. When a mailserver username is recognized
attached to a matching hostname part, its local mapping is added to the
list of local recipients.
The 'checkalias' option (normally off) extends the lookups performed by
the 'dns' keyword in multidrop mode, providing a way to cope with
remote MTAs that identify themselves using their canonical name, while
they're polled using an alias. When such a server is polled, checks to
extract the envelope address fail, and fetchmail reverts to delivery
using the To/Cc/Bcc headers (See below 'Header vs. Envelope
addresses'). Specifying this option instructs fetchmail to retrieve
all the IP addresses associated with both the poll name and the name
used by the remote MTA and to do a comparison of the IP addresses.
This comes in handy in situations where the remote server undergoes
frequent canonical name changes, that would otherwise require modifica-
tions to the rcfile. 'checkalias' has no effect if 'no dns' is speci-
fied in the rcfile.
The 'aka' option is for use with multidrop mailboxes. It allows you to
pre-declare a list of DNS aliases for a server. This is an optimiza-
tion hack that allows you to trade space for speed. When fetchmail,
while processing a multidrop mailbox, grovels through message headers
looking for names of the mailserver, pre-declaring common ones can save
it from having to do DNS lookups. Note: the names you give as argu-
ments to 'aka' are matched as suffixes -- if you specify (say) 'aka
netaxs.com', this will match not just a hostname netaxs.com, but any
hostname that ends with '.netaxs.com'; such as (say) pop3.netaxs.com
and mail.netaxs.com.
The 'localdomains' option allows you to declare a list of domains which
fetchmail should consider local. When fetchmail is parsing address
lines in multidrop modes, and a trailing segment of a host name matches
a declared local domain, that address is passed through to the listener
or MDA unaltered (local-name mappings are not applied).
If you are using 'localdomains', you may also need to specify 'no enve-
lope', which disables fetchmail's normal attempt to deduce an envelope
address from the Received line or X-Envelope-To header or whatever
header has been previously set by 'envelope'. If you set 'no envelope'
in the defaults entry it is possible to undo that in individual entries
by using 'envelope <string>'. As a special case, 'envelope "Received"'
restores the default parsing of Received lines.
The password option requires a string argument, which is the password
to be used with the entry's server.
The 'preconnect' keyword allows you to specify a shell command to be
executed just before each time fetchmail establishes a mailserver con-
nection. This may be useful if you are attempting to set up secure POP
connections with the aid of ssh(1). If the command returns a nonzero
status, the poll of that mailserver will be aborted.
Similarly, the 'postconnect' keyword similarly allows you to specify a
shell command to be executed just after each time a mailserver connec-
tion is taken down.
The 'forcecr' option controls whether lines terminated by LF only are
given CRLF termination before forwarding. Strictly speaking RFC821
requires this, but few MTAs enforce the requirement it so this option
is normally off (only one such MTA, qmail, is in significant use at
time of writing).
The 'stripcr' option controls whether carriage returns are stripped out
of retrieved mail before it is forwarded. It is normally not necessary
to set this, because it defaults to 'on' (CR stripping enabled) when
there is an MDA declared but 'off' (CR stripping disabled) when for-
warding is via SMTP. If 'stripcr' and 'forcecr' are both on, 'stripcr'
will override.
The 'pass8bits' option exists to cope with Microsoft mail programs that
stupidly slap a "Content-Transfer-Encoding: 7bit" on everything. With
this option off (the default) and such a header present, fetchmail
declares BODY=7BIT to an ESMTP-capable listener; this causes problems
for messages actually using 8-bit ISO or KOI-8 character sets, which
will be garbled by having the high bits of all characters stripped. If
'pass8bits' is on, fetchmail is forced to declare BODY=8BITMIME to any
ESMTP-capable listener. If the listener is 8-bit-clean (as all the
major ones now are) the right thing will probably result.
The 'dropstatus' option controls whether nonempty Status and X-Mozilla-
Status lines are retained in fetched mail (the default) or discarded.
Retaining them allows your MUA to see what messages (if any) were
marked seen on the server. On the other hand, it can confuse some new-
mail notifiers, which assume that anything with a Status line in it has
been seen. (Note: the empty Status lines inserted by some buggy POP
servers are unconditionally discarded.)
The 'dropdelivered' option controls whether Delivered-To headers will
be kept in fetched mail (the default) or discarded. These headers are
added by Qmail and Postfix mailservers in order to avoid mail loops but
may get in your way if you try to "mirror" a mailserver within the same
domain. Use with caution.
The 'mimedecode' option controls whether MIME messages using the
quoted-printable encoding are automatically converted into pure 8-bit
data. If you are delivering mail to an ESMTP-capable, 8-bit-clean lis-
tener (that includes all of the major MTAs like sendmail), then this
will automatically convert quoted-printable message headers and data
into 8-bit data, making it easier to understand when reading mail. If
your e-mail programs know how to deal with MIME messages, then this
option is not needed. The mimedecode option is off by default, because
doing RFC2047 conversion on headers throws away character-set informa-
tion and can lead to bad results if the encoding of the headers differs
from the body encoding.
The 'idle' option is intended to be used with IMAP servers supporting
the RFC2177 IDLE command extension, but does not strictly require it.
If it is enabled, and fetchmail detects that IDLE is supported, an IDLE
will be issued at the end of each poll. This will tell the IMAP server
to hold the connection open and notify the client when new mail is
available. If IDLE is not supported, fetchmail will simulate it by
periodically issuing NOOP. If you need to poll a link frequently, IDLE
can save bandwidth by eliminating TCP/IP connects and LOGIN/LOGOUT
sequences. On the other hand, an IDLE connection will eat almost all of
your fetchmail's time, because it will never drop the connection and
allow other polls to occur unless the server times out the IDLE. It
also doesn't work with multiple folders; only the first folder will
ever be polled.
The 'properties' option is an extension mechanism. It takes a string
argument, which is ignored by fetchmail itself. The string argument
may be used to store configuration information for scripts which
require it. In particular, the output of '--configdump' option will
make properties associated with a user entry readily available to a
Python script.
Miscellaneous Run Control Options
The words 'here' and 'there' have useful English-like significance.
Normally 'user eric is esr' would mean that mail for the remote user
'eric' is to be delivered to 'esr', but you can make this clearer by
saying 'user eric there is esr here', or reverse it by saying 'user esr
here is eric there'
Legal protocol identifiers for use with the 'protocol' keyword are:
auto (or AUTO) (legacy, to be removed from future release)
pop2 (or POP2) (legacy, to be removed from future release)
pop3 (or POP3)
sdps (or SDPS)
imap (or IMAP)
apop (or APOP)
kpop (or KPOP)
Legal authentication types are 'any', 'password', 'kerberos', 'ker-
beros_v4', 'kerberos_v5' and 'gssapi', 'cram-md5', 'otp', 'msn' (only
for POP3), 'ntlm', 'ssh', 'external' (only IMAP). The 'password' type
specifies authentication by normal transmission of a password (the
password may be plain text or subject to protocol-specific encryption
as in CRAM-MD5); 'kerberos' tells fetchmail to try to get a Kerberos
ticket at the start of each query instead, and send an arbitrary string
as the password; and 'gssapi' tells fetchmail to use GSSAPI authentica-
tion. See the description of the 'auth' keyword for more.
Specifying 'kpop' sets POP3 protocol over port 1109 with Kerberos V4
authentication. These defaults may be overridden by later options.
There are some global option statements: 'set logfile' followed by a
string sets the same global specified by --logfile. A command-line
--logfile option will override this. Note that --logfile is only effec-
tive if fetchmail detaches itself from the terminal and the logfile
already exists before fetchmail is run, and it overrides --syslog in
this case. Also, 'set daemon' sets the poll interval as --daemon does.
This can be overridden by a command-line --daemon option; in particular
--daemon 0 can be used to force foreground operation. The 'set postmas-
ter' statement sets the address to which multidrop mail defaults if
there are no local matches. Finally, 'set syslog' sends log messages
to syslogd(8).
DEBUGGING FETCHMAIL
Fetchmail crashing
There are various ways in that fetchmail may "crash", i. e. stop opera-
tion suddenly and unexpectedly. A "crash" usually refers to an error
condition that the software did not handle by itself. A well-known
failure mode is the "segmentation fault" or "signal 11" or "SIGSEGV" or
just "segfault" for short. These can be caused by hardware or by soft-
ware problems. Software-induced segfaults can usually be reproduced
easily and in the same place, whereas hardware-induced segfaults can go
away if the computer is rebooted, or powered off for a few hours, and
can happen in random locations even if you use the software the same
way.
For solving hardware-induced segfaults, find the faulty component and
repair or replace it. The Sig11 FAQ <http://www.bitwizard.nl/sig11/>;
may help you with details.
For solving software-induced segfaults, the developers may need a
"stack backtrace".
Enabling fetchmail core dumps
By default, fetchmail suppresses core dumps as these might contain
passwords and other sensitive information. For debugging fetchmail
crashes, obtaining a "stack backtrace" from a core dump is often the
quickest way to solve the problem, and when posting your problem on a
mailing list, the developers may ask you for a "backtrace".
1. To get useful backtraces, fetchmail needs to be installed without
getting stripped of its compilation symbols. Unfortunately, most
binary packages that are installed are stripped, and core files from
symbol-stripped programs are worthless. So you may need to recompile
fetchmail. On many systems, you can type
file `which fetchmail`
to find out if fetchmail was symbol-stripped or not. If yours was
unstripped, fine, proceed, if it was stripped, you need to recompile
the source code first. You do not usually need to install fetchmail in
order to debug it.
2. The shell environment that starts fetchmail needs to enable core
dumps. The key is the "maximum core (file) size" that can usually be
configured with a tool named "limit" or "ulimit". See the documentation
for your shell for details. In the popular bash shell, "ulimit -Sc
unlimited" will allow the core dump.
3. You need to tell fetchmail, too, to allow core dumps. To do this,
run fetchmail with the -d0 -v options. It is often easier to also add
--nosyslog -N as well.
Finally, you need to reproduce the crash. You can just start fetchmail
from the directory where you compiled it by typing ./fetchmail, so the
complete command line will start with ./fetchmail -Nvd0 --nosyslog and
perhaps list your other options.
After the crash, run your debugger to obtain the core dump. The debug-
ger will often be GNU GDB, you can then type (adjust paths as neces-
sary) gdb ./fetchmail fetchmail.core and then, after GDB has started up
and read all its files, type backtrace full, save the output (copy &
paste will do, the backtrace will be read by a human) and then type
quit to leave gdb. Note: on some systems, the core files have differ-
ent names, they might contain a number instead of the program name, or
number and name, but it will usually have "core" as part of their name.
INTERACTION WITH RFC 822
When trying to determine the originating address of a message, fetch-
mail looks through headers in the following order:
Return-Path:
Resent-Sender: (ignored if it doesn't contain an @ or !)
Sender: (ignored if it doesn't contain an @ or !)
Resent-From:
From:
Reply-To:
Apparently-From:
The originating address is used for logging, and to set the MAIL FROM
address when forwarding to SMTP. This order is intended to cope grace-
fully with receiving mailing list messages in multidrop mode. The
intent is that if a local address doesn't exist, the bounce message
won't be returned blindly to the author or to the list itself, but
rather to the list manager (which is less annoying).
In multidrop mode, destination headers are processed as follows: First,
fetchmail looks for the header specified by the 'envelope' option in
order to determine the local recipient address. If the mail is
addressed to more than one recipient, the Received line won't contain
any information regarding recipient addresses.
Then fetchmail looks for the Resent-To:, Resent-Cc:, and Resent-Bcc:
lines. If they exist, they should contain the final recipients and
have precedence over their To:/Cc:/Bcc: counterparts. If the Resent-*
lines don't exist, the To:, Cc:, Bcc: and Apparently-To: lines are
looked for. (The presence of a Resent-To: is taken to imply that the
person referred by the To: address has already received the original
copy of the mail.)
CONFIGURATION EXAMPLES
Note that although there are password declarations in a good many of
the examples below, this is mainly for illustrative purposes. We rec-
ommend stashing account/password pairs in your $HOME/.netrc file, where
they can be used not just by fetchmail but by ftp(1) and other pro-
grams.
The basic format is:
poll SERVERNAME protocol PROTOCOL username NAME password PASS-
WORD
Example:
poll pop.provider.net protocol pop3 username "jsmith" password "secret1"
Or, using some abbreviations:
poll pop.provider.net proto pop3 user "jsmith" password "secret1"
Multiple servers may be listed:
poll pop.provider.net proto pop3 user "jsmith" pass "secret1"
poll other.provider.net proto pop2 user "John.Smith" pass "My^Hat"
Here's the same version with more whitespace and some noise words:
poll pop.provider.net proto pop3
user "jsmith", with password secret1, is "jsmith" here;
poll other.provider.net proto pop2:
user "John.Smith", with password "My^Hat", is "John.Smith" here;
If you need to include whitespace in a parameter string or start the
latter with a number, enclose the string in double quotes. Thus:
poll mail.provider.net with proto pop3:
user "jsmith" there has password "4u but u can't krak this"
is jws here and wants mda "/bin/mail"
You may have an initial server description headed by the keyword
'defaults' instead of 'poll' followed by a name. Such a record is
interpreted as defaults for all queries to use. It may be overwritten
by individual server descriptions. So, you could write:
defaults proto pop3
user "jsmith"
poll pop.provider.net
pass "secret1"
poll mail.provider.net
user "jjsmith" there has password "secret2"
It's possible to specify more than one user per server. The 'user'
keyword leads off a user description, and every user specification in a
multi-user entry must include it. Here's an example:
poll pop.provider.net proto pop3 port 3111
user "jsmith" with pass "secret1" is "smith" here
user jones with pass "secret2" is "jjones" here keep
This associates the local username 'smith' with the pop.provider.net
username 'jsmith' and the local username 'jjones' with the
pop.provider.net username 'jones'. Mail for 'jones' is kept on the
server after download.
Here's what a simple retrieval configuration for a multidrop mailbox
looks like:
poll pop.provider.net:
user maildrop with pass secret1 to golux 'hurkle'='happy' snark here
This says that the mailbox of account 'maildrop' on the server is a
multidrop box, and that messages in it should be parsed for the server
user names 'golux', 'hurkle', and 'snark'. It further specifies that
'golux' and 'snark' have the same name on the client as on the server,
but mail for server user 'hurkle' should be delivered to client user
'happy'.
Note that fetchmail, until version 6.3.4, did NOT allow full
user@domain specifications here, these would never match. Fetchmail
6.3.5 and newer support user@domain specifications on the left-hand
side of a user mapping.
Here's an example of another kind of multidrop connection:
poll pop.provider.net localdomains loonytoons.org toons.org
envelope X-Envelope-To
user maildrop with pass secret1 to * here
This also says that the mailbox of account 'maildrop' on the server is
a multidrop box. It tells fetchmail that any address in the loony-
toons.org or toons.org domains (including sub-domain addresses like
'joe AT daffy.org') should be passed through to the local SMTP
listener without modification. Be careful of mail loops if you do
this!
Here's an example configuration using ssh and the plugin option. The
queries are made directly on the stdin and stdout of imapd via ssh.
Note that in this setup, IMAP authentication can be skipped.
poll mailhost.net with proto imap:
plugin "ssh %h /usr/sbin/imapd" auth ssh;
user esr is esr here
THE USE AND ABUSE OF MULTIDROP MAILBOXES
Use the multiple-local-recipients feature with caution -- it can bite.
All multidrop features are ineffective in ETRN and ODMR modes.
Also, note that in multidrop mode duplicate mails are suppressed. A
piece of mail is considered duplicate if it has the same message-ID as
the message immediately preceding and more than one addressee. Such
runs of messages may be generated when copies of a message addressed to
multiple users are delivered to a multidrop box.
Header vs. Envelope addresses
The fundamental problem is that by having your mailserver toss several
peoples' mail in a single maildrop box, you may have thrown away poten-
tially vital information about who each piece of mail was actually
addressed to (the 'envelope address', as opposed to the header
addresses in the RFC822 To/Cc headers - the Bcc is not available at the
receiving end). This 'envelope address' is the address you need in
order to reroute mail properly.
Sometimes fetchmail can deduce the envelope address. If the mailserver
MTA is sendmail and the item of mail had just one recipient, the MTA
will have written a 'by/for' clause that gives the envelope addressee
into its Received header. But this doesn't work reliably for other
MTAs, nor if there is more than one recipient. By default, fetchmail
looks for envelope addresses in these lines; you can restore this
default with -E "Received" or 'envelope Received'.
As a better alternative, some SMTP listeners and/or mail servers insert
a header in each message containing a copy of the envelope addresses.
This header (when it exists) is often 'X-Original-To', 'Delivered-To'
or 'X-Envelope-To'. Fetchmail's assumption about this can be changed
with the -E or 'envelope' option. Note that writing an envelope header
of this kind exposes the names of recipients (including blind-copy
recipients) to all receivers of the messages, so the upstream must
store one copy of the message per recipient to avoid becoming a privacy
problem.
Postfix, since version 2.0, writes an X-Original-To: header which con-
tains a copy of the envelope as it was received.
Qmail and Postfix generally write a 'Delivered-To' header upon deliver-
ing the message to the mail spool and use it to avoid mail loops.
Qmail virtual domains however will prefix the user name with a string
that normally matches the user's domain. To remove this prefix you can
use the -Q or 'qvirtual' option.
Sometimes, unfortunately, neither of these methods works. That is the
point when you should contact your ISP and ask them to provide such an
envelope header, and you should not use multidrop in this situation.
When they all fail, fetchmail must fall back on the contents of To/Cc
headers (Bcc headers are not available - see below) to try to determine
recipient addressees -- and these are unreliable. In particular, mail-
ing-list software often ships mail with only the list broadcast address
in the To header.
Note that a future version of fetchmail may remove To/Cc parsing!
When fetchmail cannot deduce a recipient address that is local, and the
intended recipient address was anyone other than fetchmail's invoking
user, mail will get lost. This is what makes the multidrop feature
risky without proper envelope information.
A related problem is that when you blind-copy a mail message, the Bcc
information is carried only as envelope address (it's removed from the
headers by the sending mail server, so fetchmail can see it only if
there is an X-Envelope-To header). Thus, blind-copying to someone who
gets mail over a fetchmail multidrop link will fail unless the the
mailserver host routinely writes X-Envelope-To or an equivalent header
into messages in your maildrop.
In conclusion, mailing lists and Bcc'd mail can only work if the server
you're fetching from
(1) stores one copy of the message per recipient in your domain and
(2) records the envelope information in a special header (X-Origi-
nal-To, Delivered-To, X-Envelope-To).
Good Ways To Use Multidrop Mailboxes
Multiple local names can be used to administer a mailing list from the
client side of a fetchmail collection. Suppose your name is 'esr', and
you want to both pick up your own mail and maintain a mailing list
called (say) "fetchmail-friends", and you want to keep the alias list
on your client machine.
On your server, you can alias 'fetchmail-friends' to 'esr'; then, in
your .fetchmailrc, declare 'to esr fetchmail-friends here'. Then, when
mail including 'fetchmail-friends' as a local address gets fetched, the
list name will be appended to the list of recipients your SMTP listener
sees. Therefore it will undergo alias expansion locally. Be sure to
include 'esr' in the local alias expansion of fetchmail-friends, or
you'll never see mail sent only to the list. Also be sure that your
listener has the "me-too" option set (sendmail's -oXm command-line
option or OXm declaration) so your name isn't removed from alias expan-
sions in messages you send.
This trick is not without its problems, however. You'll begin to see
this when a message comes in that is addressed only to a mailing list
you do not have declared as a local name. Each such message will fea-
ture an 'X-Fetchmail-Warning' header which is generated because fetch-
mail cannot find a valid local name in the recipient addresses. Such
messages default (as was described above) to being sent to the local
user running fetchmail, but the program has no way to know that that's
actually the right thing.
Bad Ways To Abuse Multidrop Mailboxes
Multidrop mailboxes and fetchmail serving multiple users in daemon mode
do not mix. The problem, again, is mail from mailing lists, which typ-
ically does not have an individual recipient address on it. Unless
fetchmail can deduce an envelope address, such mail will only go to the
account running fetchmail (probably root). Also, blind-copied users
are very likely never to see their mail at all.
If you're tempted to use fetchmail to retrieve mail for multiple users
from a single mail drop via POP or IMAP, think again (and reread the
section on header and envelope addresses above). It would be smarter
to just let the mail sit in the mailserver's queue and use fetchmail's
ETRN or ODMR modes to trigger SMTP sends periodically (of course, this
means you have to poll more frequently than the mailserver's expiry
period). If you can't arrange this, try setting up a UUCP feed.
If you absolutely must use multidrop for this purpose, make sure your
mailserver writes an envelope-address header that fetchmail can see.
Otherwise you will lose mail and it will come back to haunt you.
Speeding Up Multidrop Checking
Normally, when multiple users are declared fetchmail extracts recipient
addresses as described above and checks each host part with DNS to see
if it's an alias of the mailserver. If so, the name mappings described
in the "to ... here" declaration are done and the mail locally deliv-
ered.
This is a convenient but also slow method. To speed it up, pre-declare
mailserver aliases with 'aka'; these are checked before DNS lookups are
done. If you're certain your aka list contains all DNS aliases of the
mailserver (and all MX names pointing at it - note this may change in a
future version) you can declare 'no dns' to suppress DNS lookups
entirely and only match against the aka list.
SOCKS
Support for socks4/5 is a compile time configuration option. Once com-
piled in, fetchmail will always use the socks libraries and configura-
tion on your system, there are no run-time switches in fetchmail - but
you can still configure SOCKS: you can specify which SOCKS configura-
tion file is used in the SOCKS_CONF environment variable.
For instance, if you wanted to bypass the SOCKS proxy altogether and
have fetchmail connect directly, you could just pass
SOCKS_CONF=/dev/null in the environment, for example (add your usual
command line options - if any - to the end of this line):
env SOCKS_CONF=/dev/null fetchmail
EXIT CODES
To facilitate the use of fetchmail in shell scripts, an exit status
code is returned to give an indication of what occurred during a given
connection.
The exit codes returned by fetchmail are as follows:
0 One or more messages were successfully retrieved (or, if the -c
option was selected, were found waiting but not retrieved).
1 There was no mail awaiting retrieval. (There may have been old
mail still on the server but not selected for retrieval.) If you
do not want "no mail" to be an error condition (for instance,
for cron jobs), use a POSIX-compliant shell and add
|| [ $? -eq 1 ]
to the end of the fetchmail command line, note that this leaves
0 untouched, maps 1 to 0, and maps all other codes to 1. See
also item #C8 in the FAQ.
2 An error was encountered when attempting to open a socket to
retrieve mail. If you don't know what a socket is, don't worry
about it -- just treat this as an 'unrecoverable error'. This
error can also be because a protocol fetchmail wants to use is
not listed in /etc/services.
3 The user authentication step failed. This usually means that a
bad user-id, password, or APOP id was specified. Or it may mean
that you tried to run fetchmail under circumstances where it did
not have standard input attached to a terminal and could not
prompt for a missing password.
4 Some sort of fatal protocol error was detected.
5 There was a syntax error in the arguments to fetchmail, or a
pre- or post-connect command failed.
6 The run control file had bad permissions.
7 There was an error condition reported by the server. Can also
fire if fetchmail timed out while waiting for the server.
8 Client-side exclusion error. This means fetchmail either found
another copy of itself already running, or failed in such a way
that it isn't sure whether another copy is running.
9 The user authentication step failed because the server responded
"lock busy". Try again after a brief pause! This error is not
implemented for all protocols, nor for all servers. If not
implemented for your server, "3" will be returned instead, see
above. May be returned when talking to qpopper or other servers
that can respond with "lock busy" or some similar text contain-
ing the word "lock".
10 The fetchmail run failed while trying to do an SMTP port open or
transaction.
11 Fatal DNS error. Fetchmail encountered an error while perform-
ing a DNS lookup at startup and could not proceed.
12 BSMTP batch file could not be opened.
13 Poll terminated by a fetch limit (see the --fetchlimit option).
14 Server busy indication.
23 Internal error. You should see a message on standard error with
details.
24 - 26, 28, 29
These are internal codes and should not appear externally.
When fetchmail queries more than one host, return status is 0 if any
query successfully retrieved mail. Otherwise the returned error status
is that of the last host queried.
FILES
~/.fetchmailrc
default run control file
~/.fetchids
default location of file recording last message UIDs seen per
host.
~/.fetchmail.pid
lock file to help prevent concurrent runs (non-root mode).
~/.netrc
your FTP run control file, which (if present) will be searched for
passwords as a last resort before prompting for one interactively.
/var/run/fetchmail.pid
lock file to help prevent concurrent runs (root mode, Linux sys-
tems).
/etc/fetchmail.pid
lock file to help prevent concurrent runs (root mode, systems
without /var/run).
ENVIRONMENT
FETCHMAILHOME
If this environment variable is set to a valid and existing
directory name, fetchmail will read $FETCHMAILHOME/fetchmailrc
(the dot is missing in this case), $FETCHMAILHOME/.fetchids and
$FETCHMAILHOME/.fetchmail.pid rather than from the user's home
directory. The .netrc file is always looked for in the the
invoking user's home directory regardless of FETCHMAILHOME's
setting.
FETCHMAILUSER
If this environment variable is set, it is used as the name of
the calling user (default local name) for purposes such as mail-
ing error notifications. Otherwise, if either the LOGNAME or
USER variable is correctly set (e.g. the corresponding UID
matches the session user ID) then that name is used as the
default local name. Otherwise getpwuid(3) must be able to
retrieve a password entry for the session ID (this elaborate
logic is designed to handle the case of multiple names per
userid gracefully).
FETCHMAIL_DISABLE_CBC_IV_COUNTERMEASURE
(since v6.3.22): If this environment variable is set and not
empty, fetchmail will disable a countermeasure against an SSL
CBC IV attack (by setting SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS).
This is a security risk, but may be necessary for connecting to
certain non-standards-conforming servers. See fetchmail's NEWS
file and fetchmail-SA-2012-01.txt for details. Earlier fetch-
mail versions (v6.3.21 and older) used to disable this counter-
measure, but v6.3.22 no longer does that as a safety precaution.
FETCHMAIL_INCLUDE_DEFAULT_X509_CA_CERTS
(since v6.3.17): If this environment variable is set and not
empty, fetchmail will always load the default X.509 trusted cer-
tificate locations for SSL/TLS CA certificates, even if
--sslcertfile and --sslcertpath are given. The latter locations
take precedence over the system default locations. This is use-
ful in case there are broken certificates in the system directo-
ries and the user has no administrator privileges to remedy the
problem.
HOME_ETC
If the HOME_ETC variable is set, fetchmail will read
$HOME_ETC/.fetchmailrc instead of ~/.fetchmailrc.
If HOME_ETC and FETCHMAILHOME are both set, HOME_ETC will be
ignored.
SOCKS_CONF
(only if SOCKS support is compiled in) this variable is used by
the socks library to find out which configuration file it should
read. Set this to /dev/null to bypass the SOCKS proxy.
SIGNALS
If a fetchmail daemon is running as root, SIGUSR1 wakes it up from its
sleep phase and forces a poll of all non-skipped servers. For compati-
bility reasons, SIGHUP can also be used in 6.3.X but may not be avail-
able in future fetchmail versions.
If fetchmail is running in daemon mode as non-root, use SIGUSR1 to wake
it (this is so SIGHUP due to logout can retain the default action of
killing it).
Running fetchmail in foreground while a background fetchmail is running
will do whichever of these is appropriate to wake it up.
BUGS, LIMITATIONS, AND KNOWN PROBLEMS
Please check the NEWS file that shipped with fetchmail for more known
bugs than those listed here.
Fetchmail cannot handle user names that contain blanks after a "@"
character, for instance "demonstr@ti on". These are rather uncommon and
only hurt when using UID-based --keep setups, so the 6.3.X versions of
fetchmail won't be fixed.
Fetchmail cannot handle configurations where you have multiple accounts
that use the same server name and the same login. Any user@server com-
bination must be unique.
The assumptions that the DNS and in particular the checkalias options
make are not often sustainable. For instance, it has become uncommon
for an MX server to be a POP3 or IMAP server at the same time. There-
fore the MX lookups may go away in a future release.
The mda and plugin options interact badly. In order to collect error
status from the MDA, fetchmail has to change its normal signal handling
so that dead plugin processes don't get reaped until the end of the
poll cycle. This can cause resource starvation if too many zombies
accumulate. So either don't deliver to a MDA using plugins or risk
being overrun by an army of undead.
The --interface option does not support IPv6 and it is doubtful if it
ever will, since there is no portable way to query interface IPv6
addresses.
The RFC822 address parser used in multidrop mode chokes on some
@-addresses that are technically legal but bizarre. Strange uses of
quoting and embedded comments are likely to confuse it.
In a message with multiple envelope headers, only the last one pro-
cessed will be visible to fetchmail.
Use of some of these protocols requires that the program send unen-
crypted passwords over the TCP/IP connection to the mailserver. This
creates a risk that name/password pairs might be snaffled with a packet
sniffer or more sophisticated monitoring software. Under Linux and
FreeBSD, the --interface option can be used to restrict polling to
availability of a specific interface device with a specific local or
remote IP address, but snooping is still possible if (a) either host
has a network device that can be opened in promiscuous mode, or (b) the
intervening network link can be tapped. We recommend the use of ssh(1)
tunnelling to not only shroud your passwords but encrypt the entire
conversation.
Use of the %F or %T escapes in an mda option could open a security
hole, because they pass text manipulable by an attacker to a shell com-
mand. Potential shell characters are replaced by '_' before execution.
The hole is further reduced by the fact that fetchmail temporarily dis-
cards any suid privileges it may have while running the MDA. For maxi-
mum safety, however, don't use an mda command containing %F or %T when
fetchmail is run from the root account itself.
Fetchmail's method of sending bounces due to errors or spam-blocking
and spam bounces requires that port 25 of localhost be available for
sending mail via SMTP.
If you modify ~/.fetchmailrc while a background instance is running and
break the syntax, the background instance will die silently. Unfortu-
nately, it can't die noisily because we don't yet know whether syslog
should be enabled. On some systems, fetchmail dies quietly even if
there is no syntax error; this seems to have something to do with buggy
terminal ioctl code in the kernel.
The -f - option (reading a configuration from stdin) is incompatible
with the plugin option.
The 'principal' option only handles Kerberos IV, not V.
Interactively entered passwords are truncated after 63 characters. If
you really need to use a longer password, you will have to use a con-
figuration file.
A backslash as the last character of a configuration file will be
flagged as a syntax error rather than ignored.
The BSMTP error handling is virtually nonexistent and may leave broken
messages behind.
Send comments, bug reports, gripes, and the like to the fetchmail-devel
list <fetchmail-devel AT lists.de>
An HTML FAQ <http://fetchmail.berlios.de/fetchmail-FAQ.html>; is avail-
able at the fetchmail home page, it should also accompany your instal-
lation.
AUTHOR
Fetchmail is currently maintained by Matthias Andree and Rob Funk with
major assistance from Sunil Shetye (for code) and Rob MacGregor (for
the mailing lists).
Most of the code is from Eric S. Raymond <esr AT snark.com> . Too
many other people to name here have contributed code and patches.
This program is descended from and replaces popclient, by Carl Harris
<ceharris AT mal.com> ; the internals have become quite different, but
some of its interface design is directly traceable to that ancestral
program.
This manual page has been improved by Matthias Andree, R. Hannes Bein-
ert, and Hector Garcia.
SEE ALSO
README, README.SSL, README.SSL-SERVER, The Fetchmail FAQ <http://
www.fetchmail.info/fetchmail-FAQ.html>, mutt(1), elm(1), mail(1), send-
mail(8), popd(8), imapd(8), netrc(5).
The fetchmail home page. <http://fetchmail.berlios.de/>;
The maildrop home page. <http://www.courier-mta.org/maildrop/>;
APPLICABLE STANDARDS
Note that this list is just a collection of references and not a state-
ment as to the actual protocol conformance or requirements in fetch-
mail.
SMTP/ESMTP:
RFC 821, RFC 2821, RFC 1869, RFC 1652, RFC 1870, RFC 1983, RFC
1985, RFC 2554.
mail:
RFC 822, RFC 2822, RFC 1123, RFC 1892, RFC 1894.
POP2:
RFC 937
POP3:
RFC 1081, RFC 1225, RFC 1460, RFC 1725, RFC 1734, RFC 1939, RFC
1957, RFC 2195, RFC 2449.
APOP:
RFC 1939.
RPOP:
RFC 1081, RFC 1225.
IMAP2/IMAP2BIS:
RFC 1176, RFC 1732.
IMAP4/IMAP4rev1:
RFC 1730, RFC 1731, RFC 1732, RFC 2060, RFC 2061, RFC 2195, RFC
2177, RFC 2683.
ETRN:
RFC 1985.
ODMR/ATRN:
RFC 2645.
OTP: RFC 1938.
LMTP:
RFC 2033.
GSSAPI:
RFC 1508, RFC 1734, Generic Security Service Application Program
Interface (GSSAPI)/Kerberos/Simple Authentication and Security
Layer (SASL) Service Names <http://www.iana.org/assignments/
gssapi-service-names/>.
TLS: RFC 2595.
fetchmail fetchmail 6.3.24 fetchmail(1)
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