NAME¶
sendmail - an electronic mail transport agent
SYNOPSIS¶
sendmail [
flags] [
address ...]
newaliases
mailq [
-v]
hoststat
purgestat
smtpd
DESCRIPTION¶
Sendmail sends a message to one or more
recipients, routing the
message over whatever networks are necessary.
Sendmail does
internetwork forwarding as necessary to deliver the message to the correct
place.
Sendmail is not intended as a user interface routine; other programs
provide user-friendly front ends;
sendmail is used only to deliver
pre-formatted messages.
With no flags,
sendmail reads its standard input up to an end-of-file or
a line consisting only of a single dot and sends a copy of the message found
there to all of the addresses listed. It determines the network(s) to use
based on the syntax and contents of the addresses.
Local addresses are looked up in a file and aliased appropriately. Aliasing can
be prevented by preceding the address with a backslash. Beginning with 8.10,
the sender is included in any alias expansions, e.g., if `john' sends to
`group', and `group' includes `john' in the expansion, then the letter will
also be delivered to `john'.
Parameters¶
- -Ac
- Use submit.cf even if the operation mode does not indicate
an initial mail submission.
- -Am
- Use sendmail.cf even if the operation mode indicates an
initial mail submission.
- -Btype
- Set the body type to type. Current legal values are
7BIT or 8BITMIME.
- -ba
- Go into ARPANET mode. All input lines must end with a
CR-LF, and all messages will be generated with a CR-LF at the end. Also,
the ``From:'' and ``Sender:'' fields are examined for the name of the
sender.
- -bd
- Run as a daemon. Sendmail will fork and run in
background listening on socket 25 for incoming SMTP connections. This is
normally run from /etc/rc.
- -bD
- Same as -bd except runs in foreground.
- -bh
- Print the persistent host status database.
- -bH
- Purge expired entries from the persistent host status
database.
- -bi
- Initialize the alias database.
- -bm
- Deliver mail in the usual way (default).
- -bp
- Print a listing of the queue(s).
- -bP
- Print number of entries in the queue(s); only available
with shared memory support.
- -bs
- Use the SMTP protocol as described in RFC821 on standard
input and output. This flag implies all the operations of the -ba
flag that are compatible with SMTP.
- -bt
- Run in address test mode. This mode reads addresses and
shows the steps in parsing; it is used for debugging configuration
tables.
- -bv
- Verify names only - do not try to collect or deliver a
message. Verify mode is normally used for validating users or mailing
lists.
- -Cfile
- Use alternate configuration file. Sendmail gives up
any enhanced (set-user-ID or set-group-ID) privileges if an alternate
configuration file is specified.
- -D logfile
- Send debugging output to the indicated log file instead of
stdout.
- -dcategory.level...
- Set the debugging flag for category to level.
Category is either an integer or a name specifying the topic, and
level an integer specifying the level of debugging output desired.
Higher levels generally mean more output. More than one flag can be
specified by separating them with commas. A list of numeric debugging
categories can be found in the TRACEFLAGS file in the sendmail source
distribution.
The option -d0.1 prints the version of sendmail and the
options it was compiled with.
Most other categories are only useful with, and documented in,
sendmail's source code.
- -Ffullname
- Set the full name of the sender.
- -fname
- Sets the name of the ``from'' person (i.e., the envelope
sender of the mail). This address may also be used in the From: header if
that header is missing during initial submission. The envelope sender
address is used as the recipient for delivery status notifications and may
also appear in a Return-Path: header. -f should only be used by
``trusted'' users (normally root, daemon, and
network) or if the person you are trying to become is the same as
the person you are. Otherwise, an X-Authentication-Warning header will be
added to the message.
- -G
- Relay (gateway) submission of a message, e.g., when
rmail calls sendmail .
- -hN
- Set the hop count to N. The hop count is incremented
every time the mail is processed. When it reaches a limit, the mail is
returned with an error message, the victim of an aliasing loop. If not
specified, ``Received:'' lines in the message are counted.
- -i
- Ignore dots alone on lines by themselves in incoming
messages. This should be set if you are reading data from a file.
- -L tag
- Set the identifier used in syslog messages to the supplied
tag.
- -N dsn
- Set delivery status notification conditions to dsn,
which can be `never' for no notifications or a comma separated list of the
values `failure' to be notified if delivery failed, `delay' to be notified
if delivery is delayed, and `success' to be notified when the message is
successfully delivered.
- -n
- Don't do aliasing.
- -O option=value
- Set option option to the specified value.
This form uses long names. See below for more details.
- -ox value
- Set option x to the specified value. This
form uses single character names only. The short names are not described
in this manual page; see the Sendmail Installation and Operation
Guide for details.
- -pprotocol
- Set the name of the protocol used to receive the message.
This can be a simple protocol name such as ``UUCP'' or a protocol and
hostname, such as ``UUCP:ucbvax''.
- -q[time]
- Process saved messages in the queue at given intervals. If
time is omitted, process the queue once. Time is given as a
tagged number, with `s' being seconds, `m' being minutes (default), `h'
being hours, `d' being days, and `w' being weeks. For example, `-q1h30m'
or `-q90m' would both set the timeout to one hour thirty minutes. By
default, sendmail will run in the background. This option can be
used safely with -bd.
- -qp[time]
- Similar to -qtime, except that instead of
periodically forking a child to process the queue, sendmail forks a single
persistent child for each queue that alternates between processing the
queue and sleeping. The sleep time is given as the argument; it defaults
to 1 second. The process will always sleep at least 5 seconds if the queue
was empty in the previous queue run.
- -qf
- Process saved messages in the queue once and do not fork(),
but run in the foreground.
- -qGname
- Process jobs in queue group called name only.
- -q[!]Isubstr
- Limit processed jobs to those containing substr as a
substring of the queue id or not when ! is specified.
- -q[!]Qsubstr
- Limit processed jobs to quarantined jobs containing
substr as a substring of the quarantine reason or not when !
is specified.
- -q[!]Rsubstr
- Limit processed jobs to those containing substr as a
substring of one of the recipients or not when ! is specified.
- -q[!]Ssubstr
- Limit processed jobs to those containing substr as a
substring of the sender or not when ! is specified.
- -Q[reason]
- Quarantine a normal queue items with the given reason or
unquarantine quarantined queue items if no reason is given. This should
only be used with some sort of item matching using as described
above.
- -R return
- Set the amount of the message to be returned if the message
bounces. The return parameter can be `full' to return the entire
message or `hdrs' to return only the headers. In the latter case also
local bounces return only the headers.
- -rname
- An alternate and obsolete form of the -f flag.
- -t
- Read message for recipients. To:, Cc:, and Bcc: lines will
be scanned for recipient addresses. The Bcc: line will be deleted before
transmission.
- -V envid
- Set the original envelope id. This is propagated across
SMTP to servers that support DSNs and is returned in DSN-compliant error
messages.
- -v
- Go into verbose mode. Alias expansions will be announced,
etc.
- -X logfile
- Log all traffic in and out of mailers in the indicated log
file. This should only be used as a last resort for debugging mailer bugs.
It will log a lot of data very quickly.
- --
- Stop processing command flags and use the rest of the
arguments as addresses.
Options¶
There are also a number of processing options that may be set. Normally these
will only be used by a system administrator. Options may be set either on the
command line using the
-o flag (for short names), the
-O flag
(for long names), or in the configuration file. This is a partial list limited
to those options that are likely to be useful on the command line and only
shows the long names; for a complete list (and details), consult the
Sendmail Installation and Operation Guide. The options are:
- AliasFile=file
- Use alternate alias file.
- HoldExpensive
- On mailers that are considered ``expensive'' to connect to,
don't initiate immediate connection. This requires queueing.
- CheckpointInterval=N
- Checkpoint the queue file after every N successful
deliveries (default 10). This avoids excessive duplicate deliveries when
sending to long mailing lists interrupted by system crashes.
- DeliveryMode=x
- Set the delivery mode to x. Delivery modes are `i'
for interactive (synchronous) delivery, `b' for background (asynchronous)
delivery, `q' for queue only - i.e., actual delivery is done the next time
the queue is run, and `d' for deferred - the same as `q' except that
database lookups for maps which have set the -D option (default for the
host map) are avoided.
- ErrorMode=x
- Set error processing to mode x. Valid modes are `m'
to mail back the error message, `w' to ``write'' back the error message
(or mail it back if the sender is not logged in), `p' to print the errors
on the terminal (default), `q' to throw away error messages (only exit
status is returned), and `e' to do special processing for the BerkNet. If
the text of the message is not mailed back by modes `m' or `w' and if the
sender is local to this machine, a copy of the message is appended to the
file dead.letter in the sender's home directory.
- SaveFromLine
- Save UNIX-style From lines at the front of messages.
- MaxHopCount=N
- The maximum number of times a message is allowed to ``hop''
before we decide it is in a loop.
- IgnoreDots
- Do not take dots on a line by themselves as a message
terminator.
- SendMimeErrors
- Send error messages in MIME format. If not set, the DSN
(Delivery Status Notification) SMTP extension is disabled.
- ConnectionCacheTimeout=timeout
- Set connection cache timeout.
- ConnectionCacheSize=N
- Set connection cache size.
- LogLevel=n
- The log level.
- MeToo=False
- Don't send to ``me'' (the sender) if I am in an alias
expansion.
- CheckAliases
- Validate the right hand side of aliases during a
newaliases(1) command.
- OldStyleHeaders
- If set, this message may have old style headers. If not
set, this message is guaranteed to have new style headers (i.e., commas
instead of spaces between addresses). If set, an adaptive algorithm is
used that will correctly determine the header format in most cases.
- QueueDirectory=queuedir
- Select the directory in which to queue messages.
- StatusFile=file
- Save statistics in the named file.
- Timeout.queuereturn=time
- Set the timeout on undelivered messages in the queue to the
specified time. After delivery has failed (e.g., because of a host being
down) for this amount of time, failed messages will be returned to the
sender. The default is five days.
- UserDatabaseSpec=userdatabase
- If set, a user database is consulted to get forwarding
information. You can consider this an adjunct to the aliasing mechanism,
except that the database is intended to be distributed; aliases are local
to a particular host. This may not be available if your sendmail does not
have the USERDB option compiled in.
- ForkEachJob
- Fork each job during queue runs. May be convenient on
memory-poor machines.
- SevenBitInput
- Strip incoming messages to seven bits.
- EightBitMode=mode
- Set the handling of eight bit input to seven bit
destinations to mode: m (mimefy) will convert to seven-bit MIME
format, p (pass) will pass it as eight bits (but violates protocols), and
s (strict) will bounce the message.
- MinQueueAge=timeout
- Sets how long a job must ferment in the queue between
attempts to send it.
- DefaultCharSet=charset
- Sets the default character set used to label 8-bit data
that is not otherwise labelled.
- DialDelay=sleeptime
- If opening a connection fails, sleep for sleeptime
seconds and try again. Useful on dial-on-demand sites.
- NoRecipientAction=action
- Set the behaviour when there are no recipient headers (To:,
Cc: or Bcc:) in the message to action: none leaves the message
unchanged, add-to adds a To: header with the envelope recipients,
add-apparently-to adds an Apparently-To: header with the envelope
recipients, add-bcc adds an empty Bcc: header, and add-to-undisclosed adds
a header reading `To: undisclosed-recipients:;'.
- MaxDaemonChildren=N
- Sets the maximum number of children that an incoming SMTP
daemon will allow to spawn at any time to N.
- ConnectionRateThrottle=N
- Sets the maximum number of connections per second to the
SMTP port to N.
In aliases, the first character of a name may be a vertical bar to cause
interpretation of the rest of the name as a command to pipe the mail to. It
may be necessary to quote the name to keep
sendmail from suppressing
the blanks from between arguments. For example, a common alias is:
- msgs: "|/usr/bin/msgs -s"
Aliases may also have the syntax ``:include:
filename'' to ask
sendmail to read the named file for a list of recipients. For example,
an alias such as:
- poets: ":include:/usr/local/lib/poets.list"
would read
/usr/local/lib/poets.list for the list of addresses making up
the group.
Sendmail returns an exit status describing what it did. The codes are
defined in <
sysexits.h>:
- EX_OK
- Successful completion on all addresses.
- EX_NOUSER
- User name not recognized.
- EX_UNAVAILABLE
- Catchall meaning necessary resources were not
available.
- EX_SYNTAX
- Syntax error in address.
- EX_SOFTWARE
- Internal software error, including bad arguments.
- EX_OSERR
- Temporary operating system error, such as ``cannot
fork''.
- EX_NOHOST
- Host name not recognized.
- EX_TEMPFAIL
- Message could not be sent immediately, but was queued.
If invoked as
newaliases,
sendmail will rebuild the alias
database. If invoked as
mailq,
sendmail will print the contents
of the mail queue. If invoked as
hoststat,
sendmail will print
the persistent host status database. If invoked as
purgestat,
sendmail will purge expired entries from the persistent host status
database. If invoked as
smtpd,
sendmail will act as a daemon, as
if the
-bd option were specified.
NOTES¶
sendmail often gets blamed for many problems that are actually the result
of other problems, such as overly permissive modes on directories. For this
reason,
sendmail checks the modes on system directories and files to
determine if they can be trusted. Although these checks can be turned off and
your system security reduced by setting the
DontBlameSendmail option,
the permission problems should be fixed. For more information, see:
http://www.sendmail.org/tips/DontBlameSendmail.html
FILES¶
Except for the file
/etc/mail/sendmail.cf itself the following pathnames
are all specified in
/etc/mail/sendmail.cf. Thus, these values are only
approximations.
-
/etc/mail/aliases
- raw data for alias names
-
/etc/mail/aliases.db
- data base of alias names
-
/etc/mail/sendmail.cf
- configuration file
-
/etc/mail/helpfile
- help file
-
/var/lib/sendmail/sendmail.st
- collected statistics
-
/var/spool/mqueue/*
- temp files
SEE ALSO¶
binmail(1),
mail(1),
rmail(1),
syslog(3),
aliases(5),
mailaddr(7), rc(8)
DARPA Internet Request For Comments
RFC819,
RFC821,
RFC822.
Sendmail Installation and Operation Guide, No. 8, SMM.
http://www.sendmail.org/
US Patent Numbers 6865671, 6986037.
HISTORY¶
The
sendmail command appeared in 4.2BSD.