sendmail Command-Line Flags

sendmail Command-Line Flags

You can include one or more flags on the command line to tailor a sendmail session. This section describes some of the more frequently used flags. For a complete description of command-line flags, see Appendix B, "IRIX sendmail Reference."

Changing the Values of Configuration Options

The -o flag overrides an option in the configuration file. The override is for the current session only. In the following example, the T (timeout) option becomes two minutes for this session only:

/usr/lib/sendmail -oT2m

For a complete discussion of configuration options, see Appendix B, "IRIX sendmail Reference."

Delivery Mode

One configuration option frequently overridden on the command line is the d option, which specifies the sendmail delivery mode. The delivery mode determines how quickly mail is delivered:

i: deliver interactively (synchronously)
b: deliver in background (asynchronously)
q: queue only (don't deliver)

There are trade-offs. Mode i passes the maximum amount of information to the sender, but is rarely necessary.

Mode q puts the minimum load on your station, but if you use it, delivery may be delayed for up to the queue interval.

Mode b is probably a good compromise. However, in this mode, sendmail may initiate a large number of processes if you have a mailer that takes a long time to deliver a message.

Queue Mode

The -q flag causes sendmail to process the mail queue at regular intervals. The syntax is as follows, where time defines the interval between instances of queue processing:

-q [time]

Time is expressed in number of minutes: 15m sets the interval to 15 minutes. If time is omitted, sendmail processes the queue once and returns. The -q flag is often used in conjunction with daemon mode, described in the next subsection.

Daemon Mode

To process incoming mail over sockets, a daemon must be running. The -bd flag causes sendmail to run in daemon mode. The -bd and -q flags can be combined in one call, as in the following example:

/usr/lib/sendmail -bd -q30m

This command causes sendmail to run in daemon mode and to fork a subdaemon for queue processing every half hour.

The script for starting sendmail that is provided with IRIX includes the following command line:

/usr/lib/sendmail -bd -q15m

Verify Mode

Using the -bv flag directs sendmail to validate addresses, aliases, and mailing lists. In this mode, sendmail performs verification only. It does not try to collect or deliver a message. sendmail expands all aliases, suppresses duplicates, and displays the expanded list of names. For each name, sendmail indicates if it knows how to deliver a message to that destination.

Test Mode

The -bt flag places sendmail in test mode so that it describes how the current configuration rewrites addresses. Test mode is extremely useful for debugging modifications to the /etc/sendmail.cf configuration file. For more information, see Appendix B, "IRIX sendmail Reference."