Sendmail, 3rd Edition

Queue Groups (V8.12 and Above)

As of V8.12 sendmail it is possible to group queues according to selected criteria, and then to process each group with custom settings. This versatile ability is enabled and tuned with:

• The QUEUE_GROUP mc configuration command, which defines queue groups and sets their group properties

• The queuegroup mc feature, which allows you to select queue groups based on recipient hosts via the access database

• More sophisticated queue group selections, which you can make by writing your own rule sets

You can best tune queue groups by first understanding their limitations. We cover these topics in this section, but first we need to briefly discuss the default queue group.

The Default Queue Group

Prior to V8.12 sendmail there were no queue groups. Instead, every -q command and every queue option (such as QueueDirectory) applied to all the queue directories you had.^[5]

Beginning with V8.12, sendmail offers a way to define both multiple queue directories and a way to group them by function or specialty. For compatibility with old versions, a special queue group named mqueue is the default queue group. It takes on all the properties of every -q command, and every queue option, just like before.

When you later declare particular queue groups (as we show in the next section), those additional groups take all their properties from the default group, unless you override a particular property with a specific equate. Those equates and the command-line arguments or options ...