Electronic mail (e-mail) on the SCO OpenServer system is handled by
two distinct processes:
The Mail User Agent (MUA)
enables users to send, read, and manage mail messages,
and transfers outgoing mail to a Mail Transfer Agent.
The Mail Transfer Agent (MTA) is
the group of programs that route and deliver messages to their
destinations.
On a stand-alone system, the MUA (such as mail)
and MTA (such as sendmail) interact directly.
The MUA, acting on behalf of the sending user, contacts
the MTA, which routes the mail to the local recipient. The
recipient reads the mail by using an MUA.
On a networked system, the MTA on the sending system has
the additional task of determining whether the mail should be delivered
to a local user or sent to another machine on the network, and, if
sent to another machine, what communications channel (such as
SMTP, the Simple Mail Transport Protocol) to use.
When the MTA on the
destination system receives the mail message,
that MTA forwards the message to the appropriate user.
SCO OpenServer provides a choice of Mail Transfer Agents:
MMDF
(Multichannel Memorandum Distribution Facility), the SCO
MTA that is included with the SCO UNIX
operating system
sendmail
a commonly used alternative MTA that is also included
with the SCO operating system
MMDF offers several substantial benefits over sendmail,
including:
Configuration files that are easy to read and understand.
The ability for end users to configure their own sorting parameters.
A larger set of supported delivery agents.
For a more detailed comparison of the
differences between MMDF and sendmail, see
``Comparison of sendmail with MMDF''.
For more information on these MTAs, see
Chapter 4, ``Managing mail with MMDF'' in the Mail and Messaging Guide,
and
Chapter 5, ``sendmail administration'' in the Mail and Messaging Guide.