The $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 "internal."

$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).