sendmail(1M) sendmail(1M)
NAME [Toc] [Back]
sendmail - send mail over the Internet
SYNOPSIS [Toc] [Back]
/usr/sbin/sendmail [mode] [flags] [address ...]
DESCRIPTION [Toc] [Back]
sendmail sends a message to one or more recipients or addresses and
routes 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 specified in the command line, 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 in the command line. It determines the
network(s) to use based on the syntax and contents of the addresses,
according to information in the sendmail configuration file. The
default configuration file is /etc/mail/sendmail.cf.
Local addresses are looked up in a file and aliased appropriately, and
sendmail also supports the use of NIS and LDAP for address lookup.
Aliasing can be prevented by preceding the address with a backslash
(\). Normally the sender is not included in any alias expansions.
For example, if `john' sends to `group', and `group' includes `john'
in the expansion, then the letter will not be delivered to `john'.
If newaliases is invoked, sendmail will rebuild the alias database.
newaliases is identical to sendmail -bi. See newaliases(1M). Mail
that is temporarily undeliverable is saved in a mail queue. If mailq
is invoked, sendmail will print the contents of the mail queue. The
mail queue files are in the directory /var/spool/mqueue. mailq is
identical to sendmail -bp. See mailq(1).
For mail delivery failures, users get a Delivery Status Notification
(DSN).
Note: DSNs resulting from attempts to relay a message to one or
more recipients will contain a "Diagnostic-Code" message citing
the reasons for failure. This message will not contain the
user's address.
A non-root user does not have access to the files and databases
associated with sendmail, for example, /etc/mail/aliases,
/etc/mail/aliases.*, /etc/mail/sendmail.st, and
/etc/mail/sendmail.pid.
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Note: Only root users are privileged to kill any sendmail
process. Non-root users cannot send signals to their sendmail
process.
Arguments [Toc] [Back]
sendmail recognizes the following arguments:
mode A mode selected from those described in the "Modes"
subsection below. Only one mode can be specified. The
default is -bm.
address The address of a recipient. Several addresses can be
specified.
flags A flag selected from those described in the "Flags"
subsection below. Several flags can be specified.
Modes [Toc] [Back]
sendmail operates in one of the following modes. The default is -bm,
deliver mail in the usual way.
-ba Go into ARPANET mode. All input lines must end with a CRLF,
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.
-bD Run as a daemon, but run in foreground.
-bh Print the persistent host status database.
-bH Purge the persistent host status database.
-bi Initialize the alias database for the mail aliases file.
newaliases is identical to sendmail -bi. See
newaliases(1M).
-bm Deliver mail in the usual way (default).
-bp Print a listing of the mail queue. mailq is identical to
sendmail -bp. See mailq(1).
-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.
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-bv Verify names only; i.e, do not try to collect or deliver a
message. Verify mode is normally used for validating users
or mailing lists.
Flags [Toc] [Back]
sendmail recognizes the following flags:
-Btype Set the body type. type can be either 7BIT or
8BITMIME.
-Cfile Use alternate configuration file. sendmail refuses
to run as root if an alternate configuration file is
specified.
-dX Set debugging value to X. X can also be of the form
category.level (eg; -d56.12). A low level or
category produces less output; but a high level or
category produces more output. The default for
category is 0 and that for level is 1.
-Ffullname Set the full name of the sender.
-fname Set the name of the ``from'' person (i.e., the sender
of the mail) to name . If the user of the -f option
is not a ``trusted'' user (normally root, daemon, and
network) and if the name set using the -f option and
the login name of the person actually sending the
mail are not the same, then it results in an X-
Authentication-Warning in the mail header.
-G Relay the message without any processing.
-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 in lines by themselves in incoming
messages. This should be set if you are reading from
a file.
-Ltag Specify an identifier to be used in syslog messages.
The identifier is set to tag.
-n Do not do aliasing.
-Ndsn Set delivery status notification conditions.
Following are the valid conditions to which dsn can
be set:
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never For no notifications.
failure If delivery failed.
delay If delivery is delayed.
success When message is successfully
delivered.
-Ooption=value
Set the configuration option option to a specified
value. Options are described below in "Processing
Options."
-ox=value Set option x to a specified value. Options are
described below in "Processing Options."
-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.
-qtime 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, 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. If time is specified, sendmail will run in
background. This option can be used safely with bd.
-qIsubstr Limit processed jobs to those containing substr as a
substring of the queue id.
-qRsubstr Limit processed jobs to those containing substr as a
substring of one of the recipients.
-qSsubstr Limit processed jobs to those containing substr as a
substring of the sender.
-rname An alternate and obsolete form of the f flag.
-Rreturn Set the amount of the message to be returned if the
message bounces. The values that can be set for
return are as follows:
full To return the entire message
hdrs To return only the headers.
-t Read message for recipients. To:, Cc:, and Bcc:
lines will be scanned for recipient addresses. The
Bcc: line will be deleted before transmission.
-U Initial (user) submission. This flag should always
be set when sendmail is called from a user agent such
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as mail or elm. This flag should never be set when
called from a network delivery agent such as rmail.
-v Go into verbose mode. Alias expansions will be
announced, etc.
-Venvid Set the original envelope identification. This is
propagated across SMTP to servers that support DSN's
(delivery status notification) and is returned in
DSN-compliant error messages.
-Xlogfile Log all traffic in and out of mailers in the
indicated logfile. 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.
Processing Options [Toc] [Back]
There are various processing options available. Normally these will
only be used by a system administrator. Options may be set either on
the command line using the -o flag or in the configuration file,
/etc/mail/sendmail.cf. The options are:
AliasFile=file
Use alternate alias file.
AlertTmpFailure [Toc] [Back]
If set, sendmail logs transient error messages as
LOG_ALERT messages at Loglevel>=2, else it logs as
LOG_INFO messages at Loglevel>8.
HoldExpensive [Toc] [Back]
On mailers that are considered ``expensive'' to
connect to, do not initiate immediate connection.
This requires queuing.
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. The delivery modes are:
b background (asynchronous) delivery.
d deferred; the same as q except that database
lookups (DNS and NIS lookups) are avoided.
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i interactive (synchronous) delivery.
q queue only; expect the messages to be delivered
the next time when the queue is run.
ErrorMode=x Set error processing to mode x. The valid modes are:
e do special processing for the BerkNet.
m mail back the error message.
p print the errors on the terminal (default).
q throw away error messages (only exit status is
returned).
w ``write'' back the error message (or mail it
back if the sender is not logged in).
If the text of the message is not mailed back by
modes m or w, and if the sender is local to this
machine, then a copy of the message is appended to
the file dead.letter in the sender's home directory.
SaveFromLine [Toc] [Back]
Save UNIX -style ``From'' lines at the front of
messages.
MaxHopCount=N
Use this option to set the maximum number of times a
message is allowed to ``hop'' before it is considered
in a loop.
IgnoreDots Use this option to instruct sendmail to ignore dots
in a line by themselves as a message terminator.
SendMimeErrors [Toc] [Back]
Send error messages in MIME format.
ConnectionCacheTimeOut=timeout
Set connection cache timeout.
ConnectionCacheSize=N
Set connection cache size.
Loglevel=n Set the log level.
MeToo Send to ``me'' (the sender) also if the sender is in
an alias expansion.
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CheckAliases [Toc] [Back]
Validate the right hand side of aliases during a
newaliases command. See newaliases(1M).
OldStyleheaders [Toc] [Back]
Set this option to have old style headers in the
message. 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 the messages are to be
queued.
StatusFile=file
Use this option to save mail traffic statistics into
the specified file.
DeadLetterDrop [Toc] [Back]
Define the location of the system-wide dead.letter
file.
ConnectOnlyTo [Toc] [Back]
Override the connection address (for testing).
TrustedUser Define trusted user for changing the file ownership
and also for starting the daemon.
ControlSocketName [Toc] [Back]
Set this option to create a daemon control socket.
This socket allows an external program to control and
query status from the running sendmail daemon via a
named socket.
MaxMimeHeaderLength [Toc] [Back]
Limit the size of MIME headers and parameters within
those headers. This option is intended to protect
mail user agents (MUAs) from buffer overflow attacks.
MaxAliasRecursion [Toc] [Back]
Specify the maximum depth of alias recursion.
PidFile Define the location of the pid file. The
/etc/mail/sendmail.pid file will be the default even
if this option is not set.
ProcessTitlePrefix [Toc] [Back]
Specify a prefix string for the process title shown
in ps listings.
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DataFileBufferSize [Toc] [Back]
Control the maximum size of a memory-buffered data
(df) file before a disk-based file is used.
XscriptFileBufferSize [Toc] [Back]
Control the maximum size of a memory-buffered
transcript (xf) file before a disk-based file is
used.
AuthMechanisms [Toc] [Back]
Use this option to list all the authentication
mechanisms used.
DefaultAuthInfo [Toc] [Back]
Set filename that contains authentication information
for outgoing connections. This file must contain the
user id, the authorization id, the password (plain
text), and the realm to use, each on a separate line
and must be readable by root (or the trusted user)
only. If no realm is specified, $j will be used.
AuthOptions If this option is set to 'A' then the AUTH= parameter
for the MAIL FROM command is issued only when the
authentication succeeds.
LDAPDefaultSpec [Toc] [Back]
Default map specification for LDAP maps. The value
should contain only LDAP specific settings like ``-h
host -p port -d bindDN'', etc. The settings will be
used for all LDAP maps unless they are specified in
the individual map specification (K command).
CACERTPath Path to directory with certs of CAs.
CACERTFile File containing one CA cert.
ServerCertFile [Toc] [Back]
File containing the cert of the server; i.e., this
cert is used when sendmail acts as a server.
ServerKeyFile [Toc] [Back]
File containing the private key belonging to the
server cert.
ClientCertFile [Toc] [Back]
File containing the cert of the client; i.e., this
cert is used when sendmail acts as a client.
ClientKeyFile [Toc] [Back]
File containing the private key belonging to the
client cert.
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DHParameters [Toc] [Back]
File containing the DH parameters.
RandFile File containing random data (use prefix file:) or the
name of the UNIX socket if EGD is used (use prefix
egd:).
Timeout.control [Toc] [Back]
Set this option to limit the total time spent in
satisfying a control socket request.
Timeout.resolver.retrans [Toc] [Back]
Use this option to set the resolver's retransmission
time interval in seconds. This also sets
Timeout.resolver.retrans.first and
Timeout.resolver.retrans.normal options.
Timeout.resolver.retrans.first [Toc] [Back]
Use this option to set the resolver's retransmission
time interval in seconds for the first attempt to
deliver a message.
Timeout.resolver.retrans.normal [Toc] [Back]
Use this option to set the resolver's retransmission
time interval in seconds for all resolver lookups
except the first delivery attempt.
Timeout.resolver.retry [Toc] [Back]
Use this option to set the number of times to
retransmit a resolver query. This also sets
Timeout.resolver.retry.first and
Timeout.resolver.retry.normal options.
Timeout.resolver.retry.first [Toc] [Back]
Use this option to set the number of times to
retransmit a resolver query for the first attempt to
deliver a message.
Timeout.resolver.retry.normal [Toc] [Back]
Use this option to set the number of times to
retransmit a resolver query for all resolver lookups
except the first delivery attempt.
Timeout.queuereturn=time
Use this option to set the timeout on undelivered
messages in the queue to the specified time. The
failed messages will be returned to the sender after
the delivery fails for this amount of time (e.g.,
because of a host being down). The default is three
days.
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UserDatabaseSpec=userdatabase
Set this option to get forwarding information from
the user database. You can consider this as an
adjunct to the aliasing mechanism, except that the
database is intended to be distributed; aliases are
local to a particular host.
ForkEachJob Use this option to fork each job during queue runs.
This may be convenient on memory-poor machines.
SevenBitInput [Toc] [Back]
Use this option to strip incoming messages to seven
bits.
EightBitMode=mode
Set the handling of 8-bit input to 7-bit
destinations. Mode can be set to the following
values:
m Convert to 7-bit MIME format.
p Pass it as eight bits.
s Bounce the mail.
MInQueueAge=timeout
Use this option to set the time interval between
attempts to send a message from the queue.
DefaultCharSet=charset
Use this option to set the default character-set used
to label 8-bit data that is not otherwise labeled.
DialDelay=sleeptime
If opening a connection fails, sleep for sleeptime
seconds and try again. This is useful on dial-ondemand
sites.
NoRecipientAction=action
Use this option to set the behaviour when there are
no recipient headers (To:, Cc: or Bcc:) in a message
to action. The action can be set to the following
values:
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.
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add-bcc Adds an empty Bcc:
add-to-undisclosed
Adds a header reading To:undisclosed-
recipients:
MaxDaemonChildren=N
Use this option to set the maximum number of children
that an incoming SMTP daemon will allow to spawn at
any time to N.
ConnectionRateThrottle=N
Use this option to set the maximum number of
connections per second to the SMTP port to N.
AutoRebuildAliases [Toc] [Back]
Use this option to rebuild the alias database when
needed. Setting this option may cause excessive
overhead and is not recommended.
DontProbeInterfaces [Toc] [Back]
Use this option to turn off the inclusion of all the
interface names in $=w on startup. In particular, if
you have many virtual interfaces, this option speeds
up the startup. However, unless you make other
arrangements, mails sent to those addresses will
bounce. This is useful for sending mail to hosts
which have dynamically assigned names.
DontBlameSendmail=options
This options allows you to bypass some of sendmail
file security checks at the expense of system
security. This should be used only if you are aware
of the consequences. The options available for
DontBlameSendmail are:
Safe [Toc] [Back]
AssumeSafeChown
ClassFileInUnsafeDirPath
ErrorHeaderInUnsafeDirPath
GroupWritableDirPathSafe
GroupWritableForwardFileSafe
GroupWritableIncludeFileSafe
GroupWritableAliasFile
HelpFileinUnsafeDirPath
WorldWritableAliasFile
ForwardFileInGroupWritableDirPath
IncludeFileInGroupWritableDirPath
ForwardFileInUnsafeDirPath
IncludeFileInUnsafeDirPath
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ForwardFileInUnsafeDirPathSafe [Toc] [Back]
IncludeFileInUnsafeDirPathSafe
MapInUnsafeDirPath
LinkedAliasFileInWritableDir
LinkedClassFileInWritableDir
LinkedForwardFileInWritableDir
LinkedIncludeFileInWritableDir
LinkedMapInWritableDir
LinkedServiceSwitchFileInWritableDir
FileDeliveryToHardLink
FileDeliveryToSymLink
WriteMapToHardLink
WriteMapToSymLink
WriteStatsToHardLink
WriteStatsToSymLink
RunProgramInUnsafeDirPath
RunWritableProgram
DontInitGroups=True|False
Set this option to true, to prevent program
deliveries from picking up extra group privileges.
MaxRecipientsPerMessage=no_of_recipients
Use this option to limit the number of recipients,
no_of_recipients that will be accepted in a single
SMTP transaction. After this number is reached,
sendmail starts returning "452 Too many recipients"
to all RCPT commands. This can be used to limit the
number of recipients per envelope (in particular, to
discourage use of the server for spamming). Note: A
better approach is to restrict relaying entirely.
MaxHeadersLength=max_header_length
Use this option to specify the maximum length of the
sum of all headers, max_header_length. This can be
used to prevent a Denial-of-Service(DoS) attack.
RunAsUser=user
Use this option to enable sendmail do a setuid to
that user early in processing to avoid potential
security problems. However, this means that
/var/spool/mqueue directory owned by the user and all
.forward and :include: files must be readable by that
user, and all files to be written must be writable by
that user, and all programs will be executed by that
user. It is also incompatible with the
SafeFileEnvironment option. In other words, it may
not actually add much to security. However, it
should be useful on firewalls and other places where
users do not have accounts and the aliases file is
well constrained.
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SafeFileEnvironment=option
Files named as delivery targets must be regular files
in addition to the regular checks in order to use
this option. Also, if the option is non-null, then
it is used as the name of a directory that is used as
a chroot(2) environment for the delivery; the file
names listed in an alias or forward should include
the name of this root.
QueueSortOrder=option
Use this option to sort the queue based on the
following values:
host This makes better use of the connection
cache, but may delay more ``interactive''
messages behind large backlogs under some
circumstances. It is recommended to use
this option if you have high speed links
or do not process too many ``batch''
messages; it might not perform better, if
you are using something like PPP on a
14.4 modem.
time This option causes the queue to be sorted
strictly on the time of submission. This
might adversely affect the performance
over slow lines and on nodes with heavy
traffic. Also, this does not guarantee
that jobs will be delivered in submission
order unless you set DeliveryMode=queue
option. In general, it should be used
only on the command line, and in
conjunction with -qRhost.domain.
Filename This option sorts the queue by filename.
This avoids opening and reading each
queue file while preparing to run the
queue. This will speed up the queue
processing.
PrivacyOptions=flag
The flag can be set to the following values:
public Allow open access.
needmailhelo Insist on HELO (or EHLO) before
the MAIL command.
needexpnhelo Insist on HELO (or EHLO) before
the EXPN command.
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noexpn Disallow EXPN command totally.
needvrfyhelo Insist on HELO (or EHLO) before
the VRFY command.
novrfy Disallow VRFY command totally.
restrictmailq Restrict mailq command.
restrictqrun Restrict -q command-line flag.
noreceipts Do not return success DSN's.
goaway Disallow essentially all SMTP
status queries.
authwarnings Put X-Authentication-Warning
headers in messages if HELO was
not used inside SMTP transaction.
noverb Flag to disable the SMTP VERB
command.
noetrn Flag to disable the SMTP ETRN
command.
By default, authwarnings and restrictqrun are
enabled.
DaemonPortOptions=field1=value,field2=value,...
The fields currently supported by sendmail are:
Family The values can be either inet or
inet6. The default value is
inet.
Address IP address or hostname
Name Name of the agent (MTA or MSA)
Port Port number (for Name=MSA, the
port number should be 587)
Send Send buffer size
Receive Receive buffer size
Listen Listen queue size
M Modifier flags.
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Following are the values to which the modifier flag
can be set:
a Require authentication.
b Bind to interface through which mail has been
received.
c Pass the address for canonification.
f Enable fully qualified address for From address.
h Use name of interface for outgoing HELO command.
u Disable fully qualified address for From
address.
C Do not pass the address for canonification.
E Turn off ETRN connections.
Note: In order to use the IPv6 feature, you need
to set the DaemonPortOptions with Family=inet6.
If this option is set with Name=MSA, a separate
daemon starts at port 587 that acts as a Message
Submission Agent (MSA).
ClientPortOptions=field1=value,field2=value,...
This option is similar to DaemonPortOptions but meant for
outgoing connections. See DaemonPortOptions above for the
option values available.
Aliases [Toc] [Back]
You can set up system aliases and user forwarding. The alias and
.forward files are described in the aliases(5) manpage.
EXIT STATUS [Toc] [Back]
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.
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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.
WARNING [Toc] [Back]
Terminating and restarting the sendmail daemon may not be
instantaneous.
AUTHOR [Toc] [Back]
The sendmail command was developed by the University of California,
Berkeley, and originally appeared in BSD 4.2.
FILES [Toc] [Back]
$HOME/.forward User's mail forwarding file
$HOME/dead.letter User's failed message file
Except for the /etc/mail/sendmail.cf file and the daemon process ID
file, the below mentioned default pathnames are all specified in the
configuration file, /etc/mail/sendmail.cf. These default file names
can be overridden in the configuration file.
/etc/mail/aliases raw data for alias names
/etc/mail/aliases.db data base of alias names
/etc/mail/sendmail.cf configuration file
/usr/share/lib/sendmail.hf help file
/etc/mail/sendmail.st collected statistics
/var/spool/mqueue/* mail queue files
/etc/mail/sendmail.pid The process id of the daemon
/etc/mail/sendmail.cw The list of all hostnames that are
recognized as local, which causes
sendmail to accept mail for these
hosts and attempt local delivery
/etc/nsswitch.conf configuration file for the nameservice
switch
SEE ALSO [Toc] [Back]
elm(1), expand_alias(1), idlookup(1), mail(1), mailq(1), mailstats(1),
mailx(1), praliases(1), convert_awk(1M), identd(1M), killsm(1M),
mtail(1M), newaliases(1M), smrsh(1M). aliases(5).
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