V8 sendmail the
$m macro is used to store the
domain part of the local host’s fully qualified
name. A fully qualified name begins with the local hostname, followed
by a dot and all the components of the local DNS domain.
When V8 sendmail first starts to run, it calls
gethostname(3) to get the name of the local
machine. If that call fails, it sets that local name to be
localhost. Then sendmail
calls gethostbyname(3) or
getipnodebyname(3) to find the official name for
the local host. It then looks for the leftmost dot in the official
name, and if it finds one, everything from the first character
following that dot to the end of the name then becomes the value for
host.domain ↑domain part made the value of $m
$m is initialized before the configuration file is
read. Consequently, it can be redefined in the configuration file or
as a part of the command line. Because
generally does not change once it is defined, you need not prefix it
$& when using it in rules.
$m is the NIS domain for pre-V8 versions of
Sun sendmail, and
$m is the
original user address for IDA sendmail.