The $s macro contains the
name of the sender's machine (host).
$s is given the name of the local host as its
value when sendmail starts, unless the
-p command-line switch (-p) is used, in which case $s
is given the value specified by that switch. Thereafter,
$s is given a new value by
sendmail only if the mail message was received
via SMTP. For bounced mail, the $s value is always
The s macro is intended for use in the
Received: header definition:
HReceived: $?sfrom $s $.by $j$?r with $r$. id $i
The phrase from host will be
included in this header line if $s has any value.
Here, host is the name of the sending machine.
The value in $s is saved to the
qf file when the mail message is queued and
restored to $s when the queue is later processed.
$s is transient. It can be defined on the command
line but should not be defined in the configuration file. Note that a
$& prefix is necessary when you reference this
macro in rules (that is, use $&s, not