An MTA's job is to forward mail messages to a destination machine and ultimately to deliver each message into the correct mailbox. Typically, an MTA provides a flexible array of routing and configuration features to allow administrators to cope with complex mail routing issues.
The MTA for UnixWare is a popular technology known as sendmail. A VTCL-based configuration tool is provided, which supplies a graphical interface for use in the desktop environment. Also supplied is a full screen character mode for use in character terminal environments. UnixWare supports a default environment sendmail that will work on the Internet (or a LAN) without the need for further configuration.
UnixWare provides m4(1) macros, unmodified from the original Berkeley sendmail distribution, to generate a sendmail configuration file (sendmail.cf) that is not compatible with the scoadmin(1M) graphical administration tool. However, these macros are available for those administrators who wish to use them. They are supplied under the directory /etc/mail/cf.
The sendmail MTA provides the following special features:
It is possible to have one physical machine appear as several names on the Internet. This is provided because many people want their email address to be user@mycompany.com. Without virtual domain support, a separate computer would need to be purchased for each company name. This feature, and how to configure it, are respectively described in ``Managing virtual domains'' and ``The Virtual Domain User Manager''.
A channel is analogous to a sendmail mailer, with the addition of a mechanism that determines if an address is destined for that particular channel. Channels, and how to configure them, are respectively described in ``Managing mail channels'' and ``Mail delivery channels''.
A domain table is essentially a mapping table that allows an email address of the form user@domain1 to be mapped to user@domain2. The table can contain multiple entries that map one domain to another.
UnixWare supports standard mail aliasing. In addition, it supplies a separate alias file for each virtual domain configured on the system.
slocal(1) is the local delivery agent. It provides maildelivery(4) support for incoming mail filtering according to specified selection criteria. (Also supplied is the less sophisticated forward(4) filtering mechanism.) See ``Automatic disposition (filtering) of incoming mail'' for more details of slocal.
(For much more detail on sendmail internals and configuration file formats, refer to sendmail, Bryan Costales with Eric Allman, O'Reilly & Associates, Inc.)