$r macro stores the name of the protocol that is
used when a mail message is first received. If mail is received via
SMTP or ESMTP, $r is set accordingly. Incoming
UUCP mail sets $r to
"UUCP" (using the
-p switch). With V8.7, bounced mail will now
assign $r the value
$r is intended for use only in the
Received: header definition:
HReceived: $?sfrom $s $.by $j$?r with $r$. id $i
The value in $r is saved to the
qf file when the mail message is queued, and it is
restored to $r when the queue is later processed.
$r should never be trusted, and should never be
used in rules to make policy decisions.
$r is transient. It can be defined on the command
line but should not be defined in the configuration file. Under V8
the -p switch (-p) is
the recommended way to assign a value to $r.
Note that a $& prefix is necessary when you
reference this macro in rules (that is, use
$&r, not $r).