rmail program is the dispatcher part of the UUCP
suite of software. UUCP is an old-style means of moving email between
machines that were only connected with dial-up modems. Although UUCP
has almost entirely evaporated from most of the world, it still
remains useful. The rmail program is a
restricted form of the /bin/mail program that
also understands UUCP routing.
For those rare sites that still run UUCP,
sendmail offers a replacement for the frequently
broken rmail program. The source in the
rmail directory is not suitable for all
operating systems. It is the original 4.4BSD source and will work as
is only on 4.4BSD-based systems. It is included in the
sendmail distribution as a starting point for
porting to other versions of Unix.
We won't detail how to build and use the
rmail program here. If you need it, you should
know why you do and, therefore, should have some ideas about how to
port it. If you don't run UUCP, or if you do and
have no problems, you can skip rmail.