The $n macro contains
the name of the person who returns failed mail. Traditionally, that
value is the name MAILER-DAEMON.
When delivery fails, notification of that failure is sent to the
originating sender. The sendmail program
generates a new message header, where the sender of the error mail
message (and the sender in the envelope) is taken from
$n. Then, sendmail includes
the original header and all error information in the body, but might
or might not include the original body in the bounce message (-R).
The $n macro must contain either a real
user's name or a name that resolves to a real user
through aliasing. If sendmail cannot resolve
$n to a real user, the following message is
Can't parse myself!
and the returned error mail message is saved in the file defined by
the DeadLetterDrop option (DeadLetterDrop), if that option is defined. Otherwise,
sendmail converts the qf
file into a Qf file (Section 11.5).
When an error mail message is sent, $f ($f) is given the value of $n.
Prior to V8.7, $n must be
defined in the configuration file. Beginning with V8.7
sendmail, $n is automatically
defined as MAILER-DAEMON when sendmail first
Beginning with V8.7 sendmail, you can redefine
$n in your mc configuration
file with a line such as this:
But be aware that many software programs view the name MAILER-DAEMON
as special. By changing that name, you might break the way bounces
are handled on your, or other, machines.
Because $n generally does not change once it is
defined, you need not prefix it with $& when
using it in rules.