HP-UX Mailing Services Administrator's Guide

Mailing Services Overview
Chapter 118
(MUA), communicate with a Mail Transport Agent (MTA) to send mail
messages to the appropriate destination, and receive messages destined
to the end user’s mailbox.
An MUA is a program that allows users to compose and read electronic
mail messages. The MUA provides an interface between the user and the
MTA. An outgoing mail is eventually delivered to an MTA for delivery,
and the incoming messages are collected from the MTA.
An MTA is a program that is responsible for delivering electronic mail
messages. Upon receiving a message from an MUA or another MTA, an
MTA stores the message locally, analyzes the recipients, and either
delivers the message (for local addresses) or forwards the message to
another MTA for routing. In either case, the MTA can edit and add to the
message headers.
HP-UX systems use the Sendmail MTA and the elm, mail, and mailx
MUAs.
Table 1-1 lists the MTA and MUAs that HP-UX 11i v2 supports.
Table 1-1 MTA and MUAs Supported on HP-UX 11i v2
MTA/MUA Description
elm elm is the electronic mail processing system for UNIX.
It is designed as an MUA to run with Sendmail to
send or receive messages. The most significant
difference between elm and other mail systems is that
it is screen-oriented.
mail/rmail mail/rmail is a customized HP program used to send
remote or local mail. It is primarily used by Sendmail
for local mail delivery.
mailx mailx is an interactive message processing system
that provides a comfortable and flexible environment
for sending and receiving messages electronically.
Sendmail Sendmail sends a message to one or more recipients
or addresses, routing the message over appropriate
networks.