FEATURE(mailertable)

Database selects new delivery agents V8.1 and later

A mailertable is a database that maps host.domain names to special delivery agent and new domain name pairs. Essentially, it provides a database hook into the parse rule set 0. Because mailertable follows handling of the local host, none of the hosts in the $=w ($=w on page 876) will be looked up with this feature.

New domain names that result from a mailertable lookup are used for routing but are not reflected in the headers of messages.

To illustrate, one mapping in a source text file could look like this:

compuserv.com    smtp:compuserve.com

The key portion (on the left) must be either a fully qualified host and domain name, such as lady.bcx.com, or a partial domain specification with a leading dot, such as .bcx.com. On the right, the delivery agent name must be separated from the new domain name by a colon. The source text file is converted into a database with the makemap(1) program (The makemap Program on page 370). Beginning with V8.8 sendmail, the host part of the return value can also specify a user:

downhost.com     smtp:postmaster@mailhub.our.domain
                          ↑
                     V8.8 and later

The host.domain is looked up in the mailertable database, and if that host.domain is found, a delivery agent, colon, and domain pair are returned. If the delivery agent (in mailertable) is error, the #error delivery agent is called. This allows error messages to be put into the database, as, for example:

badhost error:nohost mail to badhost is prohibited ...

Get sendmail, 4th Edition now with the O’Reilly learning platform.

O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.