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fetchmail(1) 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, POP3, IMAP2bis, IMAP4, and
IMAPrev1. It can also use the ESMTP ETRN extension and ODMR. (The
RFCs describing all these protocols are listed at the end of this man-
ual 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.
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. The mail will then
be delivered locally via your system's MDA (Mail Delivery Agent, usu-
ally sendmail(8) but your system may use a different one such as
smail, mmdf, exim, or qmail). All the delivery-control mechanisms
(such as .forward files) normally available through your system MDA
and local delivery agents will therefore work automatically.
If no port 25 listener is available, but your fetchmail configuration
was told about a reliable local MDA, it will use that MDA for local
delivery instead. At build time, fetchmail normally looks for exe-
cutable procmail(1) and sendmail(1) binaries.
If the program fetchmailconf is available, it will assist you in set-
ting up and editing a fetchmailrc configuration. It runs under X and
requires that the language Python and the Tk toolkit 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 pro-
vides complete control of fetchmail configuration, including the mul-
tidrop 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
-V | --version
Displays the version information for your copy of fetchmail.
No mail fetch is performed. Instead, for each server speci-
fied, 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 positive if you leave read but undeleted mail in your
server mailbox 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 over-
rides this.
-v | --verbose
Verbose mode. All control messages passed between fetchmail
and the mailserver are echoed to stdout. Overrides --silent.
Doubling this option (-v -v) causes extra diagnostic informa-
tion to be printed.
Disposal Options
-a | --all
(Keyword: fetchall) 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.
-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.
-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
POP3/IMAP only. Delete old (previously retrieved) messages
from the mailserver before retrieving new messages. This option
does not work with ETRN or ODMR. Warning: if your local MTA
hangs and fetchmail is aborted, the next time you run fetch-
mail, it will delete mail that was never delivered to you.
What you probably want is the default setting: if you don't
specify '-k', then fetchmail will automatically delete messages
after successful delivery.
Protocol and Query Options
-p | --protocol
(Keyword: proto[col]) Specify the protocol to use when communi-
cating with the remote mailserver. If no protocol is speci-
fied, 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
POP3 Post Office Protocol 3
APOP Use POP3 with old-fashioned MD5-challenge authentica-
tion.
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 autodetects
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
mailbox 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 RFC1725).
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 run-
ning in daemon mode.
-P | --port
(Keyword: port) The port option permits you to specify a TCP/IP
port to connect on. This option will seldom be necessary as
all the supported protocols have well-established default port
numbers.
--principal
(Keyword: principal) The principal option permits you to spec-
ify a service principal for mutual authentication. This is
applicable to POP3 or IMAP with Kerberos authentication.
-t | --timeout
(Keyword: timeout) The timeout option allows you to set a
server-nonresponse timeout in seconds. If a mailserver does
not send a greeting message or respond to commands for the
given number of seconds, fetchmail will hang up on it. Without
such a timeout fetchmail might hang up indefinitely trying to
fetch mail from a down host. This would be particularly annoy-
ing for a fetchmail running in background. There is a default
timeout which fetchmail -V will report. If a given connection
receives too many timeouts in succession, fetchmail will con-
sider it wedged and stop retrying, the calling user will be
notified by email if this happens.
--plugin
(Keyword: plugin) The plugin option allows you to use an exter-
nal program to establish the TCP connection. This is useful if
you want to use socks, SSL, ssh, or need some special fire-
walling 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 token must be bounded by whites-
pace or beginning of string or end of string). Fetchmail will
write to the plugin's stdin and read from the plugin's stdout.
--plugout
(Keyword: plugout) Identical to the plugin option above, but
this one is used for the SMTP connections (which will probably
not need it, so it has been separated from plugin).
-r | --folder
(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 available under POP3, ETRN, or ODMR.
--tracepolls
(Keyword: tracepolls) Tell fetchail to poll trace information
in the form 'polling %s account %s' to the Received line it
generates, where the %s parts are replaced by the user's remote
name and the poll label (the Received header also normally
includes the server's truename). This can be used to facilate
mail filtering based on the account it is being received from.
--ssl (Keyword: ssl) Causes the connection to the mail server to be
encrypted via SSL. Connect to the server using the specified
base protocol over a connection secured by SSL. SSL support
must be present at the server. If no port is specified, the
connection is attempted to the well known port of the SSL ver-
sion of the base protocol. This is generally a different port
than the port used by the base protocol. For IMAP, this is
port 143 for the clear protocol and port 993 for the SSL
secured protocol.
--sslcert
(Keyword: sslcert) Specifies the file name of the client side
public SSL certificate. Some SSL encrypted servers may require
client side keys and certificates for authentication. 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. Some
servers may require it, some servers may request it but not
require it, and some servers may not request it at all. It may
be the same file as the private key (combined key and certifi-
cate file) but this is not recommended.
--sslkey
(Keyword: sslkey) Specifies the file name of the client side
private SSL key. Some SSL encrypted servers may require client
side keys and certificates 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. Some servers may
require it, some servers may request it but not require it, and
some servers may not request it at all. It may be the same
file as the public key (combined key and certificate file) but
this is not recommended. 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.
--sslproto
(Keyword: sslproto) Forces an ssl protocol. Possible values are
'ssl2', 'ssl3' and 'tls1'. Try this if the default handshake
does not work for your server.
--sslcertck
(Keyword: sslcertck) Causes fetchmail to strictly check the
server certificate against a set of local trusted certificates
(see the sslcertpath option). If the server certificate is not
signed by one of the trusted ones (directly or indirectly), the
SSL connection will fail. This checking should prevent man-in-
the-middle attacks against the SSL connection. Note that CRLs
are seemingly not currently supported by OpenSSL in certificate
verification! Your system clock should be reasonably accurate
when using this option!
--sslcertpath
(Keyword: sslcertpath) Sets the directory fetchmail uses to
look up local certificates. The default is your OpenSSL default
one. The directory must be hashed as 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/ subdirectory).
--sslfingerprint
(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, fetch-
mail will compare the server key fingerprint with the given
one, and the connection will fail if they do not match. This
can be used to prevent man-in-the-middle attacks.
Delivery Control Options
-S | --smtphost
(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 for-
warding target for the current run. Normally, 'localhost' is
added to the end of the list as an invisible default. However,
when using Kerberos authentication, the FQDN of the machine
running fetchmail is added to the end of the list as an invisi-
ble 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 25 (or ''smtp'' under IPv6). If
you specify an absolute pathname (beginning with a /), it will
be interpreted as the name of a UNIX socket accepting LMTP con-
nections (such as is supported by the Cyrus IMAP daemon) Exam-
ple:
--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
(Keyword: fetchdomains) In ETRN or ODMR mode, this option spec-
ifies 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 fetchmail.
-D | --smtpaddress
(Keyword: smtpaddress) Specify the domain to be appended to
addresses in RCPT TO lines shipped to SMTP. The name of the
SMTP server (as specified by --smtphost, or defaulted to
"localhost") is used when this is not specified.
--smtpname
(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 | --antispam
(Keyword: antispam) Specifies the list of numeric SMTP errors
that are to be interpreted as a spam-block response from the
listener. A value of -1 disables this option. For the com-
mand-line option, the list values should be comma-separated.
-m | --mda
(Keyword: mda) You can force mail to be passed to an MDA
directly (rather than forwarded to port 25) with the --mda or
-m option. To avoid losing mail, use this option only with
MDAs like procmail or sendmail that return a nonzero status on
disk-full and other resource-exhaustion errors; the nonzero
status tells fetchmail that delivery failed and prevents the
message from being deleted off the server. If fetchmail is
running as root, it sets its userid to that of the target user
while delivering mail through an MDA. Some possible MDAs are
"/usr/sbin/sendmail -i -f %F %T", "/usr/bin/deliver" and
"/usr/bin/procmail -d %T" (but the latter is usually redundant
as it's what SMTP listeners normally forward to). Local deliv-
ery 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. In both cases the addresses
are enclosed 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 like "sendmail -i -t"
that dispatches on the contents of To/Cc/Bcc, it will create
mail loops and bring the just wrath of many postmasters down
upon your head. Also, do not try to combine multidrop mode
with an MDA such as procmail that can only accept one
addressee; you will lose.
--lmtp (Keyword: lmtp) Cause delivery via LMTP (Local Mail Transfer
Protocol). A service port must be explicitly specified (with a
slash suffix) on each host in the smtphost hunt list if this
option is selected; the default port 25 will (in accordance
with RFC 2033) not be accepted.
--bsmtp
(keyword: bsmtp) Append fetched mail to a BSMTP file. This
simply contains the SMTP commands that would normally be gener-
ated by fetchmail when passing mail to an SMTP listener daemon.
An argument of '-' causes the mail to be written to standard
output. 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.
Resource Limit Control Options
-l | --limit
(Keyword: limit) Takes a maximum octet size argument. Messages
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
--flush, it can be used to delete oversized messages waiting on
a server. In daemon mode, oversize notifications are mailed to
the calling user (see the --warnings option). This option does
not work with ETRN or ODMR.
-w | --warnings
(Keyword: warnings) Takes an interval in seconds. When you
call fetchmail with a 'limit' option in daemon mode, this con-
trols the interval at which warnings about oversized messages
are mailed to the calling 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, renotification is suppressed until after
the warning interval elapses (it will take place at the end of
the first following poll).
-b | --batchlimit
(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 ini-
tiates delivery of a message 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 produce annoying delays when fetch-
mail is processing very large batches. Setting the batch limit
to some nonzero size will prevent these delays. This option
does not work with ETRN or ODMR.
-B | --fetchlimit
(Keyword: fetchlimit) Limit the number of messages accepted
from a given server in a single poll. By default there is no
limit. An explicit --fetchlimit of 0 overrides any limits set
in your run control file. This option does not work with ETRN
or ODMR.
--fetchsizelimit
(Keyword: fetchsizelimit) Limit the number of sizes of messages
accepted from a given server in a single transaction. This
option is useful in reducing 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 down-
loaded at the start. This option does not work with ETRN or
ODMR. For POP3, the only valid non-zero value is 1.
--fastuidl
(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 number 'n' indicates how rarely a linear search
should be done. In daemon mode, linear search is used once fol-
lowed 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. This option
works with POP3 only.
-e | --expunge
(keyword: expunge) Arrange for deletions to be made final after
a given number of messages. Under POP2 or POP3, fetchmail can-
not make deletions final without sending QUIT and ending the
session -- with this option on, fetchmail will break a long
mail retrieval session into multiple subsessions, sending QUIT
after each sub-session. This is a good defense against line
drops on POP3 servers that do not do the equivalent of a QUIT
on hangup. Under IMAP, fetchmail normally issues an EXPUNGE
command after each deletion in order to force the deletion to
be done immediately. 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 | --username
(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 fetch-
mail. See USER AUTHENTICATION below for a complete descrip-
tion.
-I | --interface
(Keyword: interface) Require that a specific interface device
be up and have a specific local or remote IP 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 pass-
word may be vulnerable to snooping (especially 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 specified 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.
-M | --monitor
(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 interval, 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 interface 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 collected.
--auth
(Keyword: auth[enticate]) This option permits you to specify an
authentication type (see USER AUTHENTICATION below for
details). The possible values are any, 'password', 'ker-
beros_v5' and 'kerberos' (or, for excruciating exactness, 'ker-
beros_v4'), gssapi, cram-md5, otp, ntlm, and ssh. When any
(the default) is specified, fetchmail tries first methods that
don't require a password (GSSAPI, KERBEROS_IV); then it looks
for methods that mask your password (CRAM-MD5, X-OTP, NTLM);
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
various authentication methods (ssh suppresses authentication).
Any value other than password, cram-md5, ntlm 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 gssapi or kerberos_v4 if you are using a proto-
col variant that employs GSSAPI or K4. Choosing KPOP protocol
automatically selects Kerberos authentication. This option
does not work with ETRN.
Miscellaneous Options
-f | --fetchmailrc
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 0600
(u=rw,g=,o=) or else be /dev/null.
-i | --idfile
(Keyword: idfile) Specify an alternate name for the .fetchids
file used to save POP3 UIDs.
-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 (oth-
erwise 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 generally not a good idea to
actually turn off rewrite.) When using ETRN or ODMR, the
rewrite option is ineffective.
-E | --envelope
(Keyword: envelope) This option changes the header fetchmail
assumes will carry a copy of the mail's envelope address. Nor-
mally this is 'X-Envelope-To' but as this header is not stan-
dard, 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, and it should not be necessary unless you have glob-
ally disabled Received parsing with 'no envelope' in the
.fetchmailrc file.
-Q | --qvirtual
(Keyword: qvirtual) The string prefix assigned to this option
will be removed from the user name found in the header speci-
fied with the envelope option (before doing multidrop name map-
ping 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 pre-
vent mail loops. To set up qmail to batch mail for a discon-
nected site the ISP-mailhost will have normally put that site
in its 'Virtualhosts' control file so it will add a prefix to
all mail addresses for this site. This results in mail sent to
'username@userhost.userdom.dom.com' having a 'Delivered-To:'
line of the form:
Delivered-To: mbox-userstr-username@userhost.userdom.dom.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 fetch-
mail reliably identify the original envelope recipient, but you
have to strip the 'mbox-userstr-' prefix to deliver to the cor-
rect 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 assign-
ment in the language Python. This option is meant to be used
with an interactive ~/.fetchmailrc editor like fetchmailconf,
written in Python.
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.
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. (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 adminis-
trator if you don't know the correct user-id and password for your
mailbox account.
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. 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 (the program to do this
with on the server is probably called popauth(8)). You put the same
password in your ~/.fetchmailrc file. Each time fetchmail logs in, it
sends a cryptographically secure hash of your password and the server
greeting time to the server, which can verify it by checking its
authorization database.
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 poll-
nane 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-conformant GSSAPI capa-
bility, and will use it. Currently this has only been tested over
Kerberos 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 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 (similar to APOP) is supported. If you
compile in the support, fetchmail will try to perform an RPA pass-
phrase authentication instead of sending over the password en clair if
it detects "@compuserve.com" in the hostname.
If you are using IMAP, Microsoft's NTLM authentication (used by
Microsoft Exchange) is supported. If you compile in the support,
fetchmail will try to perform an NTLM authentication (instead of send-
ing over the password en clair) whenever the server returns AUTH=NTLM
in its capability 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.
If you are using IPsec, the -T (--netsec) option can be used to pass
an IP security request to be used when outgoing IP connections are
initialized. You can also do this using the 'netsec' server option in
the .fetchmailrc file. In either case, the option value is a string
in the format accepted by the net_security_strtorequest() function of
the inet6_apps library.
You can access SSL encrypted services by specifying the --ssl option.
You can also do this using the "ssl" server option in the .fetchmailrc
file. With SSL encryption enabled, queries are initiated over a con-
nection after negotiating an SSL session. Some services, such as POP3
and IMAP, have different well known ports defined for the SSL
encrypted services. The encrypted ports will be selected automati-
cally when SSL is enabled and no explicit port is specified.
When connecting to an SSL encrypted server, the server presents a cer-
tificate to the client for validation. The certificate is checked to
verify that the common name in the certificate 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 contin-
ues. The server certificate does not need to be signed by any spe-
cific Certifying Authority and may be a "self-signed" certificate.
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 pro-
vided or if the certificate is not valid. Some servers may require
client side certificates be signed by a recognized Certifying Author-
ity. 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://www.monkey.org/~dugsong/dsniff/). Use of an ssh tunnel (see
below for some examples) is preferable if you care seriously about the
security of your mailbox.
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
The --daemon or -d option runs fetchmail in dae-
mon mode. You must specify a numeric argument which is a polling
interval in seconds.
In daemon mode, fetchmail puts itself in background and runs forever,
querying each specified host and then sleeping for the given polling
interval.
Simply invoking
fetchmail -d 900
will, therefore, poll all the hosts described in your ~/.fetchmailrc
file (except those explicitly excluded with the 'skip' verb) once
every fifteen minutes.
It is possible to set a polling interval in your ~/.fetchmailrc file
by saying 'set daemon ', where is an integer num-
ber of seconds. If you do this, fetchmail will always start in daemon
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 makes a per-user lockfile to guarantee this.
Normally, calling fetchmail with a daemon in the background sends a
wakeup signal to the daemon, forcing it to poll mailservers immedi-
ately. (The wakeup signal is SIGHUP if fetchmail is running as root,
SIGUSR1 otherwise.) The wakeup action also clears any 'wedged' flags
indicating that connections have wedged due to failed authentication
or multiple timeouts.
The option --quit will kill a running daemon process instead of waking
it up (if there is no such process, fetchmail notifies you). If the
--quit option is the only command-line option, that's all there is to
it.
The quit option may also be mixed with other command-line options; its
effect is to kill any running daemon before doing what the other
options specify in combination with the rc file.
The -L or --logfile option (keyword: set log-
file) allows you to redirect status messages emitted while detached
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 primarily useful for debugging configurations.
The --syslog option (keyword: set syslog) allows you to redirect sta-
tus 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 daemon and the results while fetching mail from the
server(s). Error messages 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, or that the -L or --logfile
<file> option was used.
The -N or --nodetach option suppresses backgrounding and detachment of
the daemon process from its control terminal. This is primarily use-
ful for debugging. Note that this also causes the logfile option to
be ignored (though perhaps it shouldn't).
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
message is fetched (and thus marked seen by the mailserver) but not
delivered 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 also that if you break
the ~/.fetchmailrc file's syntax, the new instance will softly and
silently vanish away on startup.
ADMINISTRATIVE OPTIONS
The --postmaster 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. Normally this is just 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 to be discarded.
The --nobounce option suppresses the normal action of bouncing errors
back to the sender in an RFC1894-conformant error message. If
nobounce is on, the message will go to the postmaster instead.
The --invisible option (keyword: set invisible) tries to make fetch-
mail 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 current tty is not stdout (for example log-
files). Starting with fetchmail version 5.3.0, progress dots are only
shown on stdout by default.
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 speci-
fied 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 .fetch-
mailrc, this is called 'tracepolls'.
RETRIEVAL FAILURE MODES
The protocols fetchmail uses to talk to mailservers are next to bul-
letproof. In normal operation forwarding to port 25, no message is
ever deleted (or even marked for deletion) on the host until the SMTP
listener 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 delivery error, even one due to temporary resource limits. The
well-known procmail(1) program is like this; so are most programs
designed as mail transport agents, such as sendmail(1), and exim(1).
These programs give back a reliable positive acknowledgement 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' mes-
sages, 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.
Under POP3, blame RFC1725. That version of the POP3 protocol specifi-
cation removed the LAST command, and some POP servers follow it (you
can verify this by invoking fetchmail -v to the mailserver and watch-
ing the response to LAST early in the query). The fetchmail code
tries to compensate by using POP3's UID feature, storing the identi-
fiers of messages seen in each session until the next session, in the
.fetchids file. But this doesn't track messages seen with other
clients, or read directly with a mailer on the host but not deleted
afterward. A better solution would be to switch to IMAP.
Another 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. The only real fix for this
problem is to switch 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 undocu-
mented 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. 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. This return
value is blessed by RFC1893 as "Delivery not authorized, message
refused".
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 head-
ers 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 option is on, mail that is spam-blocked triggers an
RFC1892 bounce message informing the originator that we do not accept
mail from it.
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
originator.
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.
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 com-
mand-line arguments take precedence.
To protect the security of your passwords, when --version is not on
your ~/.fetchmailrc may not have more than 0600 (u=rw,g=,o=) permis-
sions; fetchmail will complain and exit otherwise.
You may read the .fetchmailrc file as a list of commands to be exe-
cuted when fetchmail is called with no arguments.
Run Control Syntax
Comments begin with a '#' and extend through the end of the line.
Otherwise 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. deci-
mal 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). 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 standard C-style escapes (\n, \t, \b,
octal, and hex) to embed non-printable characters or string delimiters
in strings.
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 descriptions. Note: the most common cause of syntax
errors is mixing up user and server options.
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
brackets are optional. Those corresponding to command-line options
are followed by '-' and the appropriate option letter.
Here are the legal global options:
Keyword Opt Function
-------------------------------------------------------------
set daemon Set a background poll interval in
seconds
set postmaster Give the name of the last-resort
mail recipient
set no bouncemail Direct error mail to postmaster
rather than sender
set no spambounce Send spam bounces
set logfile Name of a file to dump error and
status messages to
set idfile Name of the file to store UID
lists in
set syslog Do error logging through sys-
log(3).
set no syslog Turn off error logging through
syslog(3).
set properties String value is ignored by fetch-
mail (may be used by extension
scripts)
Here are the legal server options:
Keyword Opt 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] Specify domain(s) to be regarded
as local
port -P Specify TCP/IP service port
auth[enticate] Set authentication type (default
'any')
timeout -t Server inactivity timeout in sec-
onds (default 300)
envelope -E Specify envelope-address header
name
no envelope Disable looking for envelope
address
qvirtual -Q Qmail virtual domain prefix to
remove from user name
aka 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 Enable DNS lookup for multidrop
(default)
no dns Disable DNS lookup for multidrop
checkalias Do comparison by IP address for
multidrop
no checkalias Do comparison by name for mul-
tidrop (default)
uidl -U Force POP3 to use client-side
UIDLs
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
netsec Pass in IPsec security option
request.
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.
Here are the legal user options:
Keyword Opt Function
------------------------------------------------------------
user[name] -u Set remote user name (local user
name if name 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
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 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 -o 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
flush -F Flush all seen 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)
Remember that all user options must follow all server 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 (that is, an argument of 1 selects
the second header of the given type). This is sometime useful for
ignoring bogus Received headers created by an ISP's local delivery
agent.
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', 'idle/no idle',
and 'no envelope'.
The 'via' option is for if you want to have more than one configura-
tion 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.
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.
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) the fetchmail
code does look 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 'nobounce' is on it will go to the postmaster
(which in turn defaults to being the calling user).
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 doesn't 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 deliv-
ery 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 modifi-
cations to the rcfile. 'checkalias' has no effect if 'no dns' is
specified 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 opti-
mization hack that allows you to trade space for speed. When fetch-
mail, 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 arguments to 'aka' are matched as suffixes -- if you specify (say)
'aka netaxs.com', this will match not just a hostnamed 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
envelope', 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 indi-
vidual entries by using 'envelope '. 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 nec-
essary to set this, because it defaults to 'on' (CR stripping enabled)
when there is an MDA declared but 'off' (CR stripping disabled) when
forwarding 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, fetch-
mail 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 prob-
ably 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 con-
fuse 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 wether 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
information 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 pools 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)
pop2 (or POP2)
pop3 (or POP3)
sdps (or SDPS)
imap (or IMAP)
apop (or APOP)
kpop (or KPOP)
Legal authentication types are 'any', 'password', 'kerberos', 'kere-
beros_v5' and 'gssapi', 'cram-md5', 'otp', 'ntlm', 'ssh'. The 'pass-
word' type specifies authentication by normal transmission of a pass-
word (the password may be plaintext or subject to protocol-specific
encryption as in APOP); 'kerberos' tells fetchmail to try to get a
Kerberos ticket at the start of each query instead, and send an arbi-
trary string as the password; and 'gssapi' tells fetchmail to use GSS-
API authentication. 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 currently four global option statements; 'set logfile' fol-
lowed by a string sets the same global specified by --logfile. A com-
mand-line --logfile option will override this. 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 postmaster' statement sets the
address to which multidrop mail defaults if there are no local
matches. Finally, 'set syslog' sends log messages to syslogd(8).
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
gracefully 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 Received: header (or whichever one is
specified by the 'envelope' option) 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 exists, they should contain the final recipients and
have precedence over their To:/Cc:/Bcc: counterparts. If the Resent-*
lines doesn'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
programs.
Basic format is:
poll SERVERNAME protocol PROTOCOL username NAME password PASSWORD
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 a version of those two 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;
This version is much easier to read and doesn't cost significantly
more (parsing is done only once, at startup time).
If you need to include whitespace in a parameter string, enclose the
string in double quotes. Thus:
poll mail.provider.net with proto pop3:
user "jsmith" there has password "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 (this is only
likely to be useful when running fetchmail in daemon mode as root).
The 'user' keyword leads off a user description, and every user speci-
fication 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 multi-drop 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
multi-drop box, and that messages in it should be parsed for the
server user names 'golux', 'hurkle', and 'snark'. It further speci-
fies 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'.
Here's an example of another kind of multidrop connection:
poll pop.provider.net localdomains loonytoons.org toons.org:
user maildrop with pass secret1 to * here
This also says that the mailbox of account 'maildrop' on the server is
a multi-drop box. It tells fetchmail that any address in the loony-
toons.org or toons.org domains (including subdomain addresses like
'joe@daffy.loonytoons.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
potentially vital information about who each piece of mail was actu-
ally addressed to (the 'envelope address', as opposed to the header
addresses in the RFC822 To/Cc/Bcc headers). 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 recipi-
ent, the MTA will have written a 'by/for' clause that gives the enve-
lope addressee into its Received header. But this doesn't work reli-
ably 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'.
Alternatively, 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-Envelope-To'. Fetchmail's assump-
tion 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; it is therefore regarded by some administrators as a secu-
rity/privacy problem.
A slight variation of the 'X-Envelope-To' header is the 'Delivered-To'
put by qmail to avoid mail loops. It will probably 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. When they
all fail, fetchmail must fall back on the contents of To/Cc/Bcc head-
ers to try to determine recipient addressees -- and these are not
reliable. In particular, mailing-list software often ships mail with
only the list broadcast address in the To header.
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.
A related problem is that when you blind-copy a mail message, the Bcc
information is carried only as envelope address (it's not put in the
headers fetchmail can see unless there is an X-Envelope header).
Thus, blind-copying to someone who gets mail over a fetchmail link
will fail unless the the mailserver host routinely writes X-Envelope
or an equivalent header into messages in your maildrop.
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 (send-
mail's -oXm command-line option or OXm declaration) so your name isn't
removed from alias expansions 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 typically 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 recipi-
ent 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
delivered.
This is the safest but also slowest 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) you can
declare 'no dns' to suppress DNS lookups entirely and only match
against the aka list.
EXIT CODES
To facilitate the use of fetchmail in shell scripts, an exit code is
returned to give an indication of what occurred during a given connec-
tion.
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.)
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.
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 containing 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.
15 Server timed out during an IMAP IDLE.
23 Internal error. You should see a message on standard error
with details.
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 associating hosts with last message IDs
seen (used only with newer RFC1725-compliant POP3 servers sup-
porting the UIDL command).
~/.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 interac-
tively.
/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
If the FETCHMAILUSER variable is set, it is used as the name of the
calling user (default local name) for purposes such as mailing 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 getp-
wuid(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).
If the environment variable FETCHMAILHOME is set to a valid and exist-
ing directory name, the .fetchmailrc and .fetchids and .fetchmail.pid
files are put there instead of in the invoking user's home directory
(and lose the leading dots on their names). The .netrc file is looked
for in the the invoking user's home directory regardless of FETCHMAIL-
HOME's setting.
SIGNALS
If a fetchmail daemon is running as root, SIGHUP wakes it up from its
sleep phase and forces a poll of all non-skipped servers (this is in
accordance with the usual conventions for system daemons).
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 run-
ning will do whichever of these is appropriate to wake it up.
BUGS AND KNOWN PROBLEMS
The mda and plugin options interact badly. In order to collect error
status from the MDA, fetchmail has to change its normal signal han-
dling so that dead plugin processes don't get reaped until the end of
the poll cycle. This can cause resource starvation if too many zom-
bies accumulate. So either don't deliver to a MDA using plugins or
risk being overrun by an army of undead.
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. To get around this, use a
mailserver-side filter that consolidates the contents of all envelope
headers into a single one (procmail, mailagent, or maildrop can be
programmed to do this fairly easily).
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
command. Potential shell characters are replaced by '_' before execu-
tion. The hole is further reduced by the fact that fetchmail tem-
porarily discards any suid privileges it may have while running the
MDA. For maximum 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 bouncemail and spam bounces requires
that port 25 of localhost be available for sending mail via SMTP.
If you modify a ~/.fetchmailrc while a background instance is running
and break the syntax, the background instance will die silently.
Unfortunately, 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 UIDL code is generally flaky and tends to lose its state on errors
and line drops (so that old messages are re-seen). If this happens to
you, switch to IMAP4.
The 'principal' option only handles Kerberos IV, not V.
Send comments, bug reports, gripes, and the like to the fetchmail-
friends list . An HTML FAQ is
available at the fetchmail home page; surf to
http://www.catb.org/~esr/fetchmail or do a WWW search for pages with
'fetchmail' in their titles.
AUTHOR
Eric S. Raymond . Too many other people to
name here have contributed code and patches. This program is
descended from and replaces popclient, by Carl Harris ; the internals have become quite different, but some of
its interface design is directly traceable to that ancestral program.
SEE ALSO
mutt(1), elm(1), mail(1), sendmail(8), popd(8), imapd(8), netrc(5)
APPLICABLE STANDARDS
SMTP/ESMTP:
RFC 821, RFC2821, RFC 1869, RFC 1652, RFC 1870, RFC 1983, RFC
1985, RFC 2554.
mail:
RFC 822, RFC2822, RFC 1123, RFC 1892, RFC 1894.
POP2:
RFC 937
POP3:
RFC 1081, RFC 1225, RFC 1460, RFC 1725, RFC1734, RFC 1939, RFC
1957, RFC2195, RFC 2449.
APOP:
RFC 1460, RFC 1725, 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.
TLS RFC 2595.
fetchmail(1)
UNIX/Linux commands referenced on this page:
- as
- more
- at
- links
- which
- time
- file
- play
- false
- alternatives
- sendmail
- ssh
- hostname
- write
- clear
- clock
- look
- groups
- compare
- host
- make
- addresses
- procmail
- accept
- size
- batch
- login
- link
- net
- users
- col
- who
- ping
- identify
- strip
- dump
- man
- id
- setup
- lockfile
- kill
- touch
- tty
- talk
- spam
- find
- true
- reject
- strings
- test
- convert
- less
- last
- restore
- sort
- sleep