The $f macro is used to
hold the address of the sender. That address can be obtained by
sendmail from any of a variety of places:
During an SMTP conversation the sending host specifies the address of
the sender by issuing a MAIL FROM: command.
Users and programs can specify the address of the sender by using the
-f command-line switch when running
In processing a message from the queue, the sender's
address is taken from the qf
file's S line.
In processing bounced mail, the sender becomes the name specified by
the value of $n, usually
In the absence of the preceding factors,
sendmail tries to use the user identity of the
invoking program to determine the sender.
Once sendmail has determined the sender (and
performed aliasing for a local sender), it rewrites the address found
with the canonify rule set 3, the rule set 1, and
the final rule set 4. The rewritten address is
then made the value of $f.
$f is intended for use in both configuration-file
header commands and delivery agent A= equates.
$f differs from $g in that
$g undergoes additional processing to produce a
true return address. When sendmail queues a mail
message and when it processes the queue, the values in
$f and $g are identical.
$f is transient. If it is defined in the
configuration file or in the command line, that definition can be
ignored by sendmail. Note that a
$& prefix is necessary when you reference this
macro in rules (that is, use $&f, not