sendmail, smtpd -- an electronic mail transport agent


sendmail flags address ...


sendmail sends a message to one or more recipients, routing the message over whatever networks are necessary. It 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. For example, if ``john'' sends to ``group'', and ``group'' includes ``john'' in in the expansion, then the letter will also be delivered to ``john''.


B type
Set the body type to type. Current legal values are 7BIT or 8BITMIME.

Go into ARPANET mode. All input lines must end with a Carriage return-Linefeed (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.

Run as a daemon. This requires Berkeley IPC. sendmail will fork and run in background listening on socket 25 for incoming SMTP connections. This is normally run from /etc/rc.

Same as bd, except runs in foreground.

Print the persistent host status database.

Purge expired entries from the persistent host status database.

Initialize the alias database.

Deliver mail in the usual way (default).

Print a listing of the queue.

Use the SMTP protocol as described in RFC 821 on standard input and output. This flag implies all the operations of the ba flag that are compatible with SMTP.

Run in address test mode. This mode reads addresses and shows the steps in parsing; it is used for debugging configuration tables.

Verify names only. Do not try to collect or deliver a message. Verify mode is normally used for validating users or mailing lists.

C file
Use alternate configuration file. sendmail refuses to run as root if an alternate configuration file is specified.

d X
Set debugging value to X.

F fullname
Set the full name of the sender.

f name
Sets the name of the ``from'' person (that is, the envelope sender of the mail). This address can 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 can 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.

h N
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.

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:

no notifications or a comma separated list of the values

to be notified if delivery failed

to be notified if delivery is delayed

to be notified when the message is successfully delivered

Do not do aliasing.

O option=value
Set option to the specified value. This form uses long names. See ``Options'' for more details.

o xvalue
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 UNRESOLVED XREF-0 for details.

p protocol
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]
Processed 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 the background. This option can be used safely with bd.

qI substr
Limit processed jobs to those containing substr as a substring of the queue ID.

qR substr
Limit processed jobs to those containing substr as a substring of one of the recipients.

qS substr
Limit processed jobs to those containing substr as a substring of the sender.

R return
Set the amount of the message to be returned if the message bounces. The return parameter can be

to return the entire message

to return only the headers

r name
An alternate and obsolete form of the f flag.

Read message for recipients. To:, Cc:, and Bcc: lines will be scanned for recipient addresses. The Bcc: line will be deleted before transmission. Any addresses in the argument list will be suppressed, that is, they will not receive copies even if listed in the message header.

Initial (user) submission. This should always be set when called from a user agent such as mail(1) or exmh and never be set when called by a network delivery agent such as rmail(1M).

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.

Go into verbose mode. Alias expansions will be announced, and so on.

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.


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 UNRESOLVED XREF-0.

The options are as follows:

Use alternate alias file.

On mailers that are considered ``expensive'' to connect to, do not initiate immediate connection. This requires queueing.

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.

Set the delivery mode to x. Delivery modes are

interactive (synchronous) delivery

background (asynchronous) delivery

queue only; that is, actual delivery is done the next time the queue is run

deferred; the same as q except that database lookups (notably DNS and NIS lookups) are avoided

Set error processing to mode x. Valid modes are:

mail back the error message

``write'' back the error message (or mail it back if the sender is not logged in)

print the errors on the terminal (default)

throw away error messages (only exit status is returned),

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.

Save UNIX-style From: lines at the front of messages.

The maximum number of times a message is allowed to ``hop'' before we decide it is in a loop.

Do not take dots on a line by themselves as a message terminator.

Send error messages in MIME format. If not set, the DSN (Delivery Status Notification) SMTP extension is disabled.

Set connection cache timeout.

Set connection cache size.

The log level.

Send to ``me'' (the sender) also if I am in an alias expansion.

Validate the right hand side of aliases during a newaliases(1M) command.

If set, this message may have old style headers. If not set, this message is guaranteed to have new style headers (that is, commas instead of spaces between addresses). If set, an adaptive algorithm is used that will correctly determine the header format in most cases.

Select the directory in which to queue messages.

Save statistics in the named file.

Set the timeout on undelivered messages in the queue to the specified time. After delivery has failed (for examle, because of a host being down) for this amount of time, failed messages will be returned to the sender. The default is five days.

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.

Fork each job during queue runs. May be convenient on memory-poor machines.

Strip incoming messages to seven bits.

Set the handling of eight bit input to seven bit destinations to mode:

(mimefy) will convert to seven-bit MIME format

(pass) will pass it as eight bits (but violates protocols)

(strict) will bounce the message

Sets how long a job must ferment in the queue between attempts to send it.

Sets the default character set used to label 8-bit data that is not otherwise labelled.

If opening a connection fails, sleep for sleeptime seconds and try again. Useful on dial-on-demand sites.

Set the behaviour when there are no recipient headers (To:, Cc: or Bcc:) in the message to action:

leaves the message unchanged

adds a To: header with the envelope recipients

adds an Apparently-To: header with the envelope recipients

adds an empty Bcc: header

adds a header reading ``To: undisclosed-recipients:;''

Sets the maximum number of children that an incoming SMTP daemon will allow to spawn at any time to 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:
   -literal -offset indent -compact
   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.

Exit codes

sendmail returns an exit status describing what it did. The codes are defined in <sysexits.h>:

Successful completion on all addresses.

User name not recognized.

Catchall meaning necessary resources were not available.

Syntax error in address.

Internal software error, including bad arguments.

Temporary operating system error, such as ``cannot fork''.

Host name not recognized.

Message could not be sent immediately, but was queued.
If invoked as newaliases(1M), sendmail will rebuild the alias database. If invoked as mailq(1), sendmail will print the contents of the mail queue. If invoked as hoststat(1M), sendmail will print the persistent host status database. If invoked as purgestat(1M), 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.


sendmail is sometimes implicated in problems that are actually the result of such things as 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: the sendmail web site.


Except for the file /etc/ itself and the daemon process ID file, the following pathnames are all specified in /etc/

raw data for alias names

data base of alias names

configuration file

help file

collected statistics

temp files

The process ID of the daemon


aliases(4), mailaddr(1M), mailx(1), rmail(1M), syslog(3G)

RFC819, RFC821, RFC822


For a non-networked system, the sendmail(1M) startup script /etc/mail/sendmailrc (which is linked to /etc/rc2.d/S81sendmail, /etc/rc1.d/K68sendmail, and /etc/rc0.d/K68sendmail) automatically edits the file /etc/service.switch to contain an entry which directs sendmail to only look up host names in /etc/hosts, effectively disabling DNS lookups. The sendmailrc script only attempts this auto-configuration if the /etc/service.switch file exists, and contains the following comment at the top of the file:
If the /etc/service.switch file does not exist, it is not created; if this file exists, but does not contain the # AUTO=YES comment, the file is not altered.

By default, auto-configuration is enabled. Therefore, if you want to include your own customizations, you must change the comment in the service.switch file to:

   # AUTO=NO

See UNRESOLVED XREF-0 for more information.

If you have added or removed a networking card from your hardware configuration using the Network Configuration Manager, you must stop and re-start sendmail(1M) in the case where the manager does not ask you to reboot the system. You may do so by executing the following commands:

/etc/mail/sendmailrc stop
/etc/mail/sendmailrc start

© 2004 The SCO Group, Inc. All rights reserved.
UnixWare 7 Release 7.1.4 - 25 April 2004