sendmail, 4th Edition

-f

Set sender’s address All versions

The -f command-line switch^[112] causes sendmail to take the address of the sender from the command line rather than from the envelope or message header. The -f switch is used by UUCP software and by mailing list software. The form of the -f switch is:

-faddr
-f addr

Space between the -f and the addr is optional. If addr is missing, sendmail prints the following error message and ignores the -f switch:

sendmail: option requires an argument -- f

Multiple -f switches cause sendmail to print the following error message and exit:

More than one "from" person

The behavior of this switch varies depending on the version of sendmail you are running.

Prior to V8, the uid of the user specifying the -f switch must match one of the usernames given in the T configuration command. If they do not match, sendmail silently ignores the option and determines the sender’s address in the usual ways.

From V8.1 through V8.6, the T configuration command was eliminated. If the -f or -r switch was used, and if the p (privacy) option was given authwarnings, sendmail included an X-Authentication-Warning: header in the mail message. That header warned that the identity of the sender had changed.

Beginning with V8.7 sendmail, the T was reintroduced, but in a different form (Trusted Users on page 173). First sendmail checks to see whether the user specified by the -f is the same as the login name of the user running sendmail, as would be the case for mh(1). If they are the same, sendmail ...