The MTA configuration file (imta.cnf) contains the routing and address rewriting configuration information. It defines all channels and their characteristics, the rules to route mail among those channels, and the method in which addresses are rewritten by the MTA.
The configuration file consists of two parts: domain rewriting rules and channel definitions. The domain rewriting rules appear first in the file and are separated from the channel definitions by a blank line. The channel definitions are collectively referred to as the channel table. An individual channel definition forms a channel block.
Comment lines may appear anywhere in the configuration file. A comment is introduced with an exclamation point (!) in column one. Liberal use of comments to explain what is going on is strongly encouraged. The following imta.cnf file fragment displays the use of comment lines.
! Part I: Rewrite rules ! ims-ms.my_server.siroe.com $E$U@ims-ms-daemon ! ! Part II: Channel definitions
Distinguishing between blank lines and comment lines is important. Blank lines play an important role in delimiting sections of the configuration file. Comment lines are ignored by the configuration file reading routines—they are literally “not there” as far as the routines are concerned and do not count as blank lines.
The contents of other files may be included in the configuration file. If a line is encountered with a less than sign (<) in column one, the rest of the line is treated as a file name; the file name should always be an absolute and full file path. The file is opened and its contents are spliced into the configuration file at that point. Include files may be nested up to three levels deep. The following imta.cnf file fragment includes the /usr/iplanet/server5/msg-tango/table/internet.rules file.
Any files included in the configuration file must be world-readable just as the configuration file is world-readable.