sendmail - send mail over the internet
/usr/lib/sendmail [-Ac] [-Am] [-ba] [-bD] [-bd] [-bi] [-bm] [-bp] [-bP] [-bs] [-bt] [-bv] [-B type] [-C file] [-D logfile] [-d X] [-F full-
name] [-f name] [-G] [-h N] [-L tag] [ -M xvalue] [-Nnotifications] [-n] [ -Ooption =value] [ -o xvalue] [-p protocol] [ -Q [reason]] [ -q
[time]] [-q Xstring] [-R ret] [-r name] [-t] [-V envid] [-v] [-X logfile] [ address...]
The sendmail utility sends a message to one or more people, routing the message over whatever networks are necessary. sendmail does inter-
network 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
With no flags, sendmail reads its standard input up to an EOF, or a line with a single dot, and sends a copy of the letter found there to
all of the addresses listed. It determines the network to use based on the syntax and contents of the addresses.
Local addresses are looked up in the local aliases(4) file, or in a name service as defined by the nsswitch.conf(4) file, and aliased
appropriately. In addition, if there is a .forward file in a recipient's home directory, sendmail forwards a copy of each message to the
list of recipients that file contains. Refer to the section for more information about .forward files. Aliasing can be prevented by pre-
ceding the address with a backslash.
There are several conditions under which the expected behavior is for the alias database to be either built or rebuilt. This cannot occur
under any circumstances unless root owns and has exclusive write permission to the /etc/mail/aliases* files.
If a message is found to be undeliverable, it is returned to the sender with diagnostics that indicate the location and nature of the fail-
ure; or, the message is placed in a dead.letter file in the sender's home directory.
Host Access Control
sendmail uses TCP Wrappers to restrict access to hosts. It uses the service name of sendmail for hosts_access(). For more information on
TCP Wrappers, see tcpd(1M) and hosts_access(4) in the SUNWtcpd package.
The /etc/default/sendmail file stores startup options for sendmail so that the options are not removed when a host is upgraded.
You can use the following variables in the /etc/default/sendmail startup file:
Selects additional options to be used with the client daemon, which looks in the client-only queue (/var/spool/clientmqueue) and acts
as a client queue runner. No syntax checking is done, so be careful when making changes to this variable.
Similar to the QUEUEINTERVAL option, CLIENTQUEUEINTERVAL sets the time interval for mail queue runs. However, the CLIENTQUEUEINTERVAL
option controls the functions of the client daemon, instead of the functions of the master daemon. Typically, the master daemon is able
to deliver all messages to the SMTP port. However, if the message load is too high or the master daemon is not running, then messages
go into the client-only queue, /var/spool/clientmqueue. The client daemon, which checks in the client-only queue, then acts as a client
Enables an SMTP client and server to interact immediately without waiting for the queue run intervals, which are periodic. The server
can immediately deliver the portion of its queue that goes to the specified hosts. For more information, refer to the etrn(1M) man
Selects the mode to start sendmail with. Use the -bd option or leave it undefined.
Selects additional options to be used with the master daemon. No syntax checking is done, so be careful when making changes to this
Sets the interval for mail queue runs on the master daemon. # can be a positive integer that is followed by either s for seconds, m for
minutes, h for hours, d for days, or w for weeks. The syntax is checked before sendmail is started. If the interval is negative or if
the entry does not end with an appropriate letter, the interval is ignored and sendmail starts with a queue interval of 15 minutes.
Enables one persistent queue runner that sleeps between queue run intervals, instead of a new queue runner for each queue run interval.
You can set this option to p, which is the only setting available. Otherwise, this option is not set.
Mail Filter API
sendmail supports a mail filter API called "milter". For more information, see /usr/include/libmilter/README and http://www.milter.org
The following options are supported:
-Ac Uses submit.cf even if the operation mode does not indicate an initial mail submission.
-Am Uses sendmail.cf even if the operation mode indicates an initial mail submission.
-ba Goes into ARPANET mode. All input lines must end with a <RETURN-LINEFEED>, and all messages are generated with a <RETURN-
LINEFEED> at the end. Also, the From: and Sender: fields are examined for the name of the sender.
-bd Runs as a daemon in the background, waiting for incoming SMTP connections.
-bD Runs as a daemon in the foreground, waiting for incoming SMTP connections.
-bi Initializes the aliases(4) database. Root must own and have exclusive write permission to the /etc/mail/aliases* files for
successful use of this option.
-bm Delivers mail in the usual way (default).
-bp Prints a summary of the mail queues.
-bP Prints the number of entries in the queues. This option is only available with shared memory support.
-bs Uses the SMTP protocol as described in RFC 2821. This flag implies all the operations of the -ba flag that are compatible
-bt Runs in address test mode. This mode reads addresses and shows the steps in parsing; it is used for debugging configuration
-bv Verifies names only. Does not try to collect or deliver a message. Verify mode is normally used for validating users or
-B type Indicates body type (7BIT or 8BITMIME).
-C file Uses alternate configuration file.
-D logfile Send debugging output to the indicated log file instead of stdout.
-d X Sets debugging value to X.
-f name Sets the name of the "from" person (that is, the sender of the mail).
-F fullname Sets the full name of the sender.
-G When accepting messages by way of the command line, indicates that they are for relay (gateway) submission. When this flag
is set, sendmail might complain about syntactically invalid messages, for example, unqualified host names, rather than fix-
ing them. sendmail does not do any canonicalization in this mode.
-h N Sets 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.
-L tag Sets the identifier used in syslog messages to the supplied tag.
-Mxvalue Sets macro x to the specified value.
-n Does not do aliasing.
-N notificationsTags all addresses being sent as wanting the indicated notifications, which consists of the word "NEVER" or a comma-sepa-
rated list of "SUCCESS", "FAILURE", and "DELAY" for successful delivery, failure and a message that is stuck in a queue
somwhere. The default is "FAILURE,DELAY".
-oxvalue Sets option x to the specified value. Processing Options are described below.
-Ooption=value Sets option to the specified value (for long from names). Processing Options are described below.
-p protocol Sets the sending protocol. The protocol field can be in form protocol:host to set both the sending protocol and the sending
host. For example: -pUUCP:uunet sets the sending protocol to UUCP and the sending host to uunet. Some existing programs use
-oM to set the r and s macros; this is equivalent to using -p.
-q[time] Processes saved messages in the queue at given intervals. If time is omitted, processes the queue once. time is given as a
tagged number, where s is seconds, m is minutes, h is hours, d is days, and w is weeks. For example, -q1h30m or -q90m would
both set the timeout to one hour thirty minutes.
By default, sendmail runs in the background. This option can be used safely with -bd.
-qp[time] Similar to -q[time], except that instead of periodically forking a child to process the queue, sendmail forks a single per-
sistent child for each queue that alternates between processing the queue and sleeping. The sleep time (time) is specified
as the argument; it defaults to 1 second. The process always sleeps at least 5 seconds if the queue was empty in the previ-
ous queue run.
-qf Processes saved messages in the queue once and does not fork(2), but runs in the foreground.
-qG name Processes jobs in queue group called name only.
-q[!]I substr Limits processed jobs to those containing substr as a substring of the queue ID or not when ! is specified.
-q[!]Q substr Limits processed jobs to those quarantined jobs containing substr as a substring of the quarantine reason or not when ! is
-q[!]R substr Limits processed jobs to those containing substr as a substring of one of the recipients or not when ! is specified.
-q[!]S substr Limits processed jobs to those containing substr as a substring of the sender or not when ! is specified.
-Q[reason] Quarantines a normal queue item with the given reason or unquarantines a quarantined queue item if no reason is given. This
should only be used with some sort of item matching as described above.
-r name An alternate and obsolete form of the -f flag.
-R ret Identifies the information you want returned if the message bounces. ret can be HDRS for headers only or FULL for headers
-t Reads message for recipients. To:,Cc:, and Bcc: lines are scanned for people to send to. The Bcc: line is deleted before
transmission. Any addresses in the argument list is suppressed. The NoRecipientAction Processing Option can be used to
change the behavior when no legal recipients are included in the message.
-v Goes into verbose mode. Alias expansions are announced, and so forth.
-V envid The indicated envid is passed with the envelope of the message and returned if the message bounces.
-X logfile Logs all traffic in and out of sendmail in the indicated logfile for debugging mailer problems. This produces a lot of data
very quickly and should be used sparingly.
There are a number of "random" options that can be set from a configuration file. Options are represented by a single character or by mul-
tiple character names. The syntax for the single character names of is:
This sets option x to be value. Depending on the option, value may be a string, an integer, a boolean (with legal values t, T, f, or F; the
default is TRUE), or a time interval.
The multiple character or long names use this syntax:
This sets the option Longname to be argument. The long names are beneficial because they are easier to interpret than the single character
Not all processing options have single character names associated with them. In the list below, the multiple character name is presented
first followed by the single character syntax enclosed in parentheses.
Specifies possible alias files.
AliasWait (a N)
If set, waits up to N minutes for an "@:@" entry to exist in the aliases(4) database before starting up. If it does not appear in N
minutes, issues a warning. Defaults to 10 minutes.
Allows a HELO SMTP command that does not include a host name. By default this option is disabled.
If set and more than the specified number of recipients in a single SMTP envelope are rejected, sleeps for one second after each
rejected RCPT command.
Sets the blank substitution character to c. Unquoted spaces in addresses are replaced by this character. Defaults to SPACE (that is, no
change is made).
File containing one CA cert.
Path to directory with certs of CAs.
Validates the RHS of aliases when rebuilding the aliases(4) database.
Checkpoints the queue every N (default 10) addresses sent. If your system crashes during delivery to a large list, this prevents
retransmission to any but the last N recipients.
The indicated factor fact is multiplied by the message class (determined by the Precedence: field in the user header and the P lines in
the configuration file) and subtracted from the priority. Thus, messages with a higher Priority: are favored. Defaults to 1800.
File containing the cert of the client, that is, this cert is used when sendmail acts as client.
File containing the private key belonging to the client cert.
Sets client SMTP options. The options are key=value pairs. Known keys are:
Addr Address Mask Address Mask defaults to INADDR_ANY. The address mask can be a numeric address in dot notation or a network
Family Address family (defaults to INET).
Listen Size of listen queue (defaults to 10).
Port Name/number of listening port (defaults to smtp).
RcvBufSize The size of the TCP/IP receive buffer.
SndBufSize The size of the TCP/IP send buffer.
Modifier Options (flags) for the daemon. Can be:
h Uses name of interface for HELO command.
If h is set, the name corresponding to the outgoing interface address (whether chosen by means of the Connec-
tion parameter or the default) is used for the HELO/EHLO command.
If set, colons are treated as a regular character in addresses. If not set, they are treated as the introducer to the RFC 822 "group"
syntax. This option is on for version 5 and lower configuration files.
The maximum number of open connections that are to be cached at a time. The default is 1. This delays closing the current connection
until either this invocation of sendmail needs to connect to another host or it terminates. Setting it to 0 defaults to the old behav-
ior, that is, connections are closed immediately.
The maximum amount of time a cached connection is permitted to idle without activity. If this time is exceeded, the connection is imme-
diately closed. This value should be small (on the order of ten minutes). Before sendmail uses a cached connection, it always sends a
NOOP (no operation) command to check the connection. If the NOOP command fails, it reopens the connection. This keeps your end from
failing if the other end times out. The point of this option is to be a good network neighbor and avoid using up excessive resources on
the other end. The default is five minutes.
The maximum number of connections permitted per second. After this many connections are accepted, further connections are delayed. If
not set or <= 0, there is no limit.
Define the length of the interval for which the number of incoming connections is maintained. The default is 60 seconds.
Name of the control socket for daemon management. A running sendmail daemon can be controlled through this Unix domain socket. Avail-
able commands are: help, restart, shutdown, and status. The status command returns the current number of daemon children, the free disk
space (in blocks) of the queue directory, and the load average of the machine expressed as an integer. If not set, no control socket is
available. For the sake of security, this Unix domain socket must be in a directory which is accessible only by root;
/var/spool/mqueue/.smcontrol is recommended for the socket name.
File containing certificate revocation status, useful for X.509v3 authentication.
Sets server SMTP options. The options are key=value pairs. Known keys are:
Name User-definable name for the daemon (defaults to "Daemon#"). Used for error messages and logging.
Addr Address mask (defaults INADDR_ANY).
The address mask may be a numeric address in dot notation or a network name.
Family Address family (defaults to INET).
InputMailFiltersList of input mail filters for the daemon.
Listen Size of listen queue (defaults to 10).
Modifier Options (flags) for the daemon; can be a sequence (without any delimiters) of:
a Requires authentication.
b Binds to interface through which mail has been received.
c Performs hostname canonification (.cf).
f Requires fully qualified hostname (.cf).
h Uses name of interface for HELO command.
u Allows unqualified addresses (.cf).
C Does not perform hostname canonification.
E Disallows ETRN (see RFC 2476).
Name User-definable name for the daemon (defaults to Daemon#). Used for error messages and logging.
Port Name/number of listening port (defaults to smtp).
ReceiveSize The size of the TCP/IP receive buffer.
SendSize The size of the TCP/IP send buffer.
sendmail listens on a new socket for each occurrence of the DaemonPortOptions option in a configuration file.
Sets the threshold, in bytes, before a memory-bases queue data file becomes disk-based. The default is 4096 bytes.
Defines the location of the system-wide dead.letter file, formerly hard-coded to /var/tmp/dead.letter. If this option is not set (the
default), sendmail does not attempt to save to a system-wide dead.letter file in the event it cannot bounce the mail to the user or
postmaster. Instead, it renames the qf file as it has in the past when the dead.letter file could not be opened.
Sets the default character set to use when converting unlabeled 8 bit input to MIME.
DefaultUser (ggid) or (uuid)
Sets the default group ID for mailers to run in to gid or set the default userid for mailers to uid. Defaults to 1. The value can also
be given as a symbolic group or user name.
When the system load average exceeds LA, sendmail sleeps for one second on most SMTP commands and before accepting connections.
Sets minimum time for Deliver By SMTP Service Extension (RFC 2852). If 0, no time is listed, if less than 0, the extension is not
offered, if greater than 0, it is listed as minimum time for the EHLO keyword DELIVERBY.
Delivers in mode x. Legal modes are:
i Delivers interactively (synchronously).
b Delivers in background (asynchronously).
d Deferred mode. Database lookups are deferred until the actual queue run.
q Just queues the message (delivers during queue run).
Defaults to b if no option is specified, i if it is specified but given no argument (that is, Od is equivalent to Odi).
File containing the DH parameters.
If a connection fails, waits this many seconds and tries again. Zero means "do not retry".
If set, overrides the file safety checks. This compromises system security and should not be used. See http://www.send-
mail.org/tips/DontBlameSendmail.html for more information.
If set, $[ ... $] lookups that do DNS-based lookups do not expand CNAME records.
If set, the initgroups(3C) routine is never invoked. If you set this, agents run on behalf of users only have their primary
(/etc/passwd) group permissions.
If set, sendmail does not insert the names and addresses of any local interfaces into the $=w class. If set, you must also include sup-
port for these addresses, otherwise mail to addresses in this list bounces with a configuration error.
If set, does not prune route-addr syntax addresses to the minimum possible.
If an error occurs when sending an error message, sends that "double bounce" error message to this address.
Uses 8-bit data handling. This option requires one of the following keys. The key can selected by using just the first character, but
using the full word is better for clarity.
Does any necessary conversion of 8BITMIME to 7-bit.
Passes unlabeled 8-bit input through as is.
Rejects unlabeled 8-bit input.
Appends error messages with the indicated message. If it begins with a slash, it is assumed to be the pathname of a file containing a
message (this is the recommended setting). Otherwise, it is a literal message. The error file might contain the name, email address,
and/or phone number of a local postmaster who could provide assistance to end users. If the option is missing or NULL, or if it names a
file which does not exist or which is not readable, no message is printed.
Disposes of errors using mode x. The values for x are:
e Mails back errors and gives 0 exit status always.
m Mails back errors.
p Prints error messages (default).
q No messages, just gives exit status.
w Writes back errors (mail if user not logged in).
If specified, the fallbackhost acts like a very low priority MX on every host. This is intended to be used by sites with poor network
If specified, the fallBackSmartHost is used in a last-ditch effort for each host. This is intended to be used by sites with "fake
internal DNS". That is, a company whose DNS accurately reflects the world inside that company's domain but not outside.
If set to a value greater than zero (the default is one), it suppresses the MX lookups on addresses when they are initially sorted,
that is, for the first delivery attempt. This usually results in faster envelope splitting unless the MX records are readily available
in a local DNS cache. To enforce initial sorting based on MX records set FastSplit to zero. If the mail is submitted directly from the
command line, then the value also limits the number of processes to deliver the envelopes; if more envelopes are created they are only
queued up and must be taken care of by a queue run. Since the default submission method is by way of SMTP (either from a MUA or by way
of the MSP), the value of FastSplit is seldom used to limit the number of processes to deliver the envelopes.
If set, delivers each job that is run from the queue in a separate process. Use this option if you are short of memory, since the
default tends to consume considerable amounts of memory while the queue is being processed.
Sets the path for searching for users' .forward files. The default is $z/.forward. Some sites that use the automounter may prefer to
change this to /var/forward/$u to search a file with the same name as the user in a system directory. It can also be set to a sequence
of paths separated by colons; sendmail stops at the first file it can successfully and safely open. For example, /var/for-
ward/$u:$z/.forward searches first in /var/forward/ username and then in ~username/.forward (but only if the first file does not
exist). Refer to the section for more information.
Specifies the help file for SMTP.
If an outgoing mailer is marked as being expensive, does not connect immediately.
Sets the file to use when doing "file" type access of host names.
If set, host status is kept on disk between sendmail runs in the named directory tree. If a full path is not used, then the path is
interpreted relative to the queue directory.
Ignores dots in incoming messages. This is always disabled (that is, dots are always accepted) when reading SMTP mail.
Sets the default log level to n. Defaults to 9.
Sets the macro x to value. This is intended only for use from the command line.
Type of lookup to find information about local mail boxes, defaults to pw which uses getpwnam(3C). Other types can be introduced by
adding them to the source code, see libsm/mbdb.c for details.
Tries to match recipient names using the GECOS field. This allows for mail to be delivered using names defined in the GECOS field in
/etc/passwd as well as the login name.
The maximum number of children the daemon permits. After this number, connections are rejected. If not set or <=0, there is no limit.
The maximum hop count. Messages that have been processed more than N times are assumed to be in a loop and are rejected. Defaults to
The maximum size of messages that are accepted (in bytes).
Sets the maximum length of certain MIME header field values to M characters. For some of these headers which take parameters, the maxi-
mum length of each parameter is set to N if specified. If /N is not specified, one half of M is used. By default, these values are 0,
meaning no checks are done.
When set, this limits the number of concurrent queue runner processes to N. This helps to control the amount of system resources used
when processing the queue. When there are multiple queue groups defined and the total number of queue runners for these queue groups
would exceed MaxQueueChildren then the queue groups are not all run concurrently. That is, some portion of the queue groups run concur-
rently such that MaxQueueChildren is not be exceeded, while the remaining queue groups are run later (in round robin order). See
If set, limits the maximum size of any given queue run to this number of entries. This stops reading the queue directory after this
number of entries is reached; job priority is not used. If not set, there is no limit.
This sets the default maximum number of queue runners for queue groups. Up to N queue runners work in parallel on a queue group's mes-
sages. This is useful where the processing of a message in the queue might delay the processing of subsequent messages. Such a delay
can be the result of non-erroneous situations such as a low bandwidth connection. The can be overridden on a per queue group basis by
setting the Runners option. The default is 1 when not set.
Sends to me too, even if I am in an alias expansion.
If set, allows no more than the specified number of recipients in an SMTP envelope. Further recipients receive a 452 error code and are
deferred for the next delivery attempt.
Insists on at least N blocks free on the file system that holds the queue files before accepting email by way of SMTP. If there is
insufficient space, sendmail gives a 452 response to the MAIL command. This invites the sender to try again later. The optional M is a
maximum message size advertised in the ESMTP EHLO response. It is currently otherwise unused.
Specifies the amount of time a job must sit in the queue between queue runs. This allows you to set the queue run interval low for bet-
ter responsiveness without trying all jobs in each run. The default value is 0.
Specifies the characters to be quoted in a full name phrase. &,;:() are quoted automatically.
Specifies the priority of queue runners. See nice(1).
Sets action if there are no legal recipient files in the message. The legal values are:
add-apparently-to Adds an Apparently-to: header with all the known recipients (which may expose blind recipients).
add-bcc Adds an empty Bcc: header.
add-to Adds a To: header with all the known recipients (which may expose blind recipients).
add-to-undisclosed Adds a To: undisclosed-recipients: header.
none Does nothing, that is, leaves the message as it is.
Assumes that the headers may be in old format, that is, spaces delimit names. This actually turns on an adaptive algorithm: if any
recipient address contains a comma, parenthesis, or angle bracket, it is assumed that commas already exist. If this flag is not on,
only commas delimit names. Headers are always output with commas between the names.
OperatorChars or $o
Defines the list of characters that can be used to separate the components of an address into tokens.
Specifies the filename of the pid file. The default is /var/run/sendmail.pid. The filename is macro-expanded before it is opened, and
unlinked when sendmail exits.
If set, copies of error messages are sent to the named postmaster. Only the header of the failed message is sent. Since most errors are
user problems, this is probably not a good idea on large sites, and arguably contains all sorts of privacy violations, but it seems to
be popular with certain operating systems vendors.
Sets privacy options. Privacy is really a misnomer; many of these options are just a way of insisting on stricter adherence to the SMTP
The goaway pseudo-flag sets all flags except noreceipts, restrictmailq, restrictqrun, restrictexpand, noetrn, and nobodyreturn. If
mailq is restricted, only people in the same group as the queue directory can print the queue. If queue runs are restricted, only root
and the owner of the queue directory can run the queue. The restrict-expand pseudo-flag instructs sendmail to drop privileges when the
-bv option is given by users who are neither root nor the TrustedUser so users cannot read private aliases, forwards, or :include:
files. It adds the NonRootSafeAddr to the "DontBlame-Sendmail" option to prevent misleading unsafe address warnings. It also overrides
the -v (verbose) command line option to prevent information leakage. Authentication Warnings add warnings about various conditions that
may indicate attempts to fool the mail system, such as using an non-standard queue directory.
The options can be selected from:
authwarnings Puts X-Authentication-Warning: headers in messages.
goaway Disallows essentially all SMTP status queries.
needexpnhelo Insists on HELO or EHLO command before EXPN.
needmailhelo Insists on HELO or EHLO command before MAIL.
needvrfyhelo Insists on HELO or EHLO command before VRFY.
noetrn Disallows ETRN entirely.
noexpn Disallows EXPN entirely.
noreceipts Prevents return receipts.
nobodyreturn Does not return the body of a message with DSNs.
novrfy Disallows VRFY entirely.
public Allows open access.
restrictexpand Restricts -bv and -v command line flags.
restrictmailq Restricts mailq command.
restrictqrun Restricts -q command line flag.
Prefixes the process title shown on "/usr/ucb/ps auxww" listings with string. The string is macro processed.
Uses the named dir as the queue directory.
Uses factor as the multiplier in the map function to decide when to just queue up jobs rather than run them. This value is divided by
the difference between the current load average and the load average limit (x flag) to determine the maximum message priority to be
sent. Defaults to 600000.
Defaults permissions for queue files (octal). If not set, sendmail uses 0600 unless its real and effective uid are different in which
case it uses 0644.
When the system load average exceeds LA, just queues messages (that is, does not try to send them). Defaults to eight times the number
of processors online when sendmail starts.
Sets the algorithm used for sorting the queue. Only the first character of the value is used. Legal values are host (to order by the
name of the first host name of the first recipient), filename (to order by the name of the queue file name), time (to order by the sub-
mission/creation time), random (to order randomly), modification (to order by the modification time of the qf file (older entries
first)), none (to not order), and priority (to order by message priority). Host ordering makes better use of the connection cache, but
may tend to process low priority messages that go to a single host over high priority messages that go to several hosts; it probably
shouldn't be used on slow network links. Filename and modification time ordering saves the overhead of reading all of the queued items
before starting the queue run. Creation (submission) time ordering is almost always a bad idea, since it allows large, bulk mail to go
out before smaller, personal mail, but may have applicability on some hosts with very fast connections. Random is useful if several
queue runners are started by hand which try to drain the same queue since odds are they are working on different parts of the queue at
the same time. Priority ordering is the default.
Sets the queue timeout to rtime. After this interval, messages that have not been successfully sent are returned to the sender.
Defaults to five days(5d). The optional wtime is the time after which a warning message is sent. If it is missing or 0, then no warn-
ing messages are sent.
File containing random data (use prefix file:) or the name of the UNIX socket if EGD is used (use prefix egd:). Note that Solaris sup-
ports random(7D), so this does not need to be specified.
The indicated factor fact is added to the priority (thus lowering the priority of the job) for each recipient, that is, this value
penalizes jobs with large numbers of recipients. Defaults to 30000.
When the system load average exceeds LA, refuses incoming SMTP connections. Defaults to 12 times the number of processors online when
Log interval when refusing connections for this long (default: 3h).
Tunes DNS lookups.
The indicated factor fact is added to the priority every time a job is processed. Thus, each time a job is processed, its priority is
decreased by the indicated value. In most environments this should be positive, since hosts that are down are all too often down for a
long time. Defaults to 90000.
If this option is set, a Return-Receipt-To: header causes the request of a DSN, which is sent to the envelope sender as required by RFC
1891, not to the address given in the header.
If set, becomes this user when reading and delivering mail. Intended for use of firewalls where users do not have accounts.
If set, sendmail does a chroot into this directory before writing files.
Saves Unix-style From lines at the front of headers. Normally they are assumed redundant and discarded.
If set, sends error messages in MIME format (see RFC 2045 and RFC 1344 for details). If disabled, sendmail does not return the DSN key-
word in response to an EHLO and does not do Delivery Status Notification processing as described in RFC 1891.
File containing the cert of the server, that is, this cert is used when sendmail acts as server.
File containing the private key belonging to the server cert.
Defines the path to the service-switch file. Since the service-switch file is defined in the Solaris operating environment this option
Strips input to seven bits for compatibility with old systems. This should not be necessary.
Specifies key to use for shared memory segment. If not set (or 0), shared memory is not be used. If this option is set, sendmail can
share some data between different instances. For example, the number of entries in a queue directory or the available space in a file
system. This allows for more efficient program execution, since only one process needs to update the data instead of each individual
process gathering the data each time it is required.
If set, From: lines that have embedded newlines are unwrapped onto one line.
If this option and the HostStatusDirectory option are both set, uses single thread deliveries to other hosts.
SmtpGreetingMessage or $e
Specifies the initial SMTP greeting message.
Logs statistics in the named file. By default, this is /etc/mail/sendmail.st. As root, you must touch(1) this file to enable mail-
This option can be set to True, False, Interactive, or PostMilter. If set to True, sendmail is set to super-safe when running things,
that is, always instantiate the queue file, even if you are going to attempt immediate delivery. sendmail always instantiates the queue
file before returning control to the client under any circumstances. This should really always be set to True. The Interactive value
has been introduced in 8.12 and can be used together with DeliveryMode=i. It skips some synchronization calls which are effectively
doubled in the code execution path for this mode. If set to PostMilter, sendmail defers synchronizing the queue file until any milters
have signaled acceptance of the message. PostMilter is useful only when sendmail is running as an SMTP server; in all other situations
it acts the same as True.
Specifies the file mode for queue files.
Timeout reads after time interval. The timeouts argument is a list of keyword=value pairs. All but command apply to client SMTP. For
backward compatibility, a timeout with no keyword= part is set all of the longer values. The recognized timeouts and their default val-
ues, and their minimum values specified in RFC 1123 section 5.3.2 are:
all connections for a single delivery attempt [0, unspecified]
command read [1h, 5m]
initial connect [0, unspecified]
complete control socket transaction [2m, none]
data block read [1h, 3m]
reply to final . in data [1h, 10m]
reply to DATA command [5m, 2m]
file open [60sec, none]
reply to HELO or EHLO command [5m, none]
host retry [30m, unspecified]
first attempt to connect to a host [0, unspecified]
IDENT protocol timeout [5s, none]
wait for initial greeting message [5m, 5m]
wait for reply to an LMTP LHLO command [2m, unspecified]
reply to MAIL command [10m, 5m]
reply to NOOP and VERB commands [2m, none]
undeliverable message returned [5d]
deferred warning [4h]
reply to QUIT command [2m, none]
reply to RCPT command [1h, 5m]
Resolver's retransmission time interval (in seconds) [varies]. Sets both Timeout.resolver.retrans.first and Time-
Resolver's retransmission time interval (in seconds) for the first attempt to deliver a message [varies].
Resolver's retransmission time interval (in seconds) for all look-ups except the first delivery attempt [varies].
Number of times to retransmit a resolver query [varies]. Sets both Timeout.resolver.retry.first and Timeout.resolver.retry.normal.
Number of times to retransmit a resolver query for the first attempt to deliver a message [varies].
Number of times to retransmit a resolver query for all look-ups except the first delivery attempt [varies].
reply to RSET command [5m, none]
response to an SMTP STARTTLS command [1h]
Sets the local time zone info to tzinfo, for example, "PST8PDT". Actually, if this is not set, the TZ environment variable is cleared
(so the system default is used); if set but null, the user's TZ variable is used, and if set and non-null, the TZ variable is set to
If this option is 'V', then no client verification is performed,that is, the server does not ask for a certificate.
The user parameter can be a user name (looked up in the passwd map) or a numeric user id. Trusted user for file ownership and starting
the daemon. If set, generated alias databases and the control socket (if configured) are automatically owned by this user.
If you are the "best" (that is, lowest preference) MX for a given host, you should normally detect this situation and treat that condi-
tion specially, by forwarding the mail to a UUCP feed, treating it as local, or whatever. However, in some cases (such as Internet
firewalls) you may want to try to connect directly to that host as though it had no MX records at all. Setting this option causes send-
mail to try this. The downside is that errors in your configuration are likely to be diagnosed as "host unknown" or "message timed out"
instead of something more meaningful. This option is deprecated.
UnixFromLine or $l
The "From " line used when sending to files or programs.
If set, group-writable :include: and .forward files are considered "unsafe", that is, programs and files cannot be directly referenced
from such files.
If there is an Errors-To: header, sends error messages to the addresses listed there. They normally go to the envelope sender. Use of
this option causes sendmail to violate RFC 1123. This option is not recommended and deprecated.
Uses as mail submission program, that is, allows group writable queue files if the group is the same as that of a set-group-id sendmail
Defines the name and location of the file containing User Database information.
Runs in verbose mode. If this is set, sendmail adjusts the HoldExpensive and DeliveryMode options so that all mail is delivered com-
pletely in a single job so that you can see the entire delivery process. The Verbose option should never be set in the configuration
file; it is intended for command line use only.
Sets the threshold, in bytes, before a memory-bases queue transcript file becomes disk-based. The default is 4096 bytes.
If the first character of the user name is a vertical bar, the rest of the user name is used as the name of a program to pipe the mail to.
It may be necessary to quote the name of the user to keep sendmail from suppressing the blanks from between arguments.
If invoked as newaliases, sendmail rebuilds the alias database, so long as the /etc/mail/aliases* files are owned by root and root has
exclusive write permission. If invoked as mailq, sendmail prints the contents of the mail queue.
address address of an intended recipient of the message being sent.
See largefile(5) for the description of the behavior of sendmail when encountering files greater than or equal to 2 Gbyte ( 2**31 bytes).
sendmail returns an exit status describing what it did. The codes are defined in /usr/include/sysexits.h.
EX_OK Successful completion on all addresses.
EX_NOUSER User name not recognized.
EX_UNAVAILABLE Catchall. 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.
No environment variables are used. However, sendmail's start-up script, invoked by svcadm(1M), reads /etc/default/sendmail. In this file,
if the variable ETRN_HOSTS is set, the start-up script parses this variable and invokes etrn(1M) appropriately. ETRN_HOSTS should be of the
"s1:c1.1,c1.2 s2:c2.1 s3:c3.1,c3.2,c3.3"
That is, white-space separated groups of server:client where client can be one or more comma-separated names. The :client part is optional.
server is the name of the server to prod; a mail queue run is requested for each client name. This is comparable to running:
/usr/lib/sendmail -qR client
on the host server.
Contains default settings. You can override some of the settings by command line options.
Mail aliases file (ASCII)
Database of mail aliases (binary)
Database of mail aliases (binary)
Database of mail aliases (binary)
Defines environment for sendmail
Lists users that are "trusted", that is, able to set their envelope from address using -f without generating a warning message.
Temporary files and queued mail
Temporary files and queued mail
List of recipients for forwarding messages
Describes the steps needed to compile and run a filter
See attributes(5) for descriptions of the following attributes:
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|Availability |SUNWsndmu |
svcs(1), biff(1B), mail(1), mailq(1), mailx(1), nice(1), check-hostname(1M), check-permissions(1M), etrn(1M), newaliases(1M), svcadm(1M),
fork(2), getpwnam(3C), getusershell(3C), resolver(3RESOLV), aliases(4), hosts(4), shells(4), attributes(5), largefile(5), smf(5), ran-
tcpd(1M), hosts_access(4) in the SUNWtcpd package.
RFC 2821 Simple Mail Transfer Protocol, John Klensin, April 2001.
RFC 2822 Internet Message Format, Pete Resnick, April 2001.
sendmail, Third Edition, Bryan Costales with Eric Allman, O'Reilly & Associates, Inc., 2003.
The sendmail program requires a fully qualified host name when starting. A script has been included to help verify if the host name is
defined properly (see check-hostname(1M)).
The permissions and the ownership of several directories have been changed in order to increase security. In particular, access to
/etc/mail and /var/spool/mqueue has been restricted.
Security restrictions have been placed users using .forward files to pipe mail to a program or redirect mail to a file. The default shell
(as listed in /etc/passwd) of these users must be listed in /etc/shells. This restriction does not affect mail that is being redirected to
Additional restrictions have been put in place on .forward and :include: files. These files and the directory structure that they are
placed in cannot be group- or world-writable. See check-permissions(1M).
If you have interfaces that map to domains that have MX records that point to non-local destinations, you might need to enable the Dont-
ProbeInterfaces option to enable delivery to those destinations. In its default startup behavior, sendmail probes each interface and adds
an interface's IP addresses, as well as any domains that those addresses map to, to its list of domains that are considered local. For
domains thus added, being on the list of local domains is equivalent to having a 0-preference MX record, with localhost as the MX value. If
this is not the result you want, enable DontProbeInterfaces.
The sendmail service is managed by the service management facility, smf(5), under the service identifier:
Administrative actions on this service, such as enabling, disabling, or requesting restart, can be performed using svcadm(1M). The ser-
vice's status can be queried using the svcs(1) command.
Because of cryptographic import restrictions in some countries, symmetric key cryptographic algorithms are limited to 128-bit if the SUN-
Wcry package is not installed. The SUNWcry package is not included with the Solaris software. This package is available instead as a sepa-
rate controlled download.
18 Mar 2005 sendmail(1M)