Postfix Address Classes


Postfix version 2.0 introduces the concept of address classes. This is a way of grouping recipient addresses by their delivery method. The idea comes from discussions with Victor Duchovni. Although address classes introduced a few incompatibilities they also made it possible to improve the handling of hosted domains and of unknown recipients.

This document provides information on the following topics:

What are address classes good for?

Why should you care about address classes? This is how Postfix decides what mail to accept, and how to deliver it. In other words, address classes are very important for the operation of Postfix.

An address class is defined by three items.

What address classes does Postfix implement?

Initially the list of address classes is hard coded, but this is meant to become extensible. The summary below describes the main purpose of each class, and what the relevant configuration parameters are.

The local domain class.

The virtual alias domain class.

The virtual mailbox domain class.

The relay domain class.

The default domain class.

Improvements compared to Postfix 1.1

Postfix 2.0 address classes made the following improvements possible over earlier Postfix versions:

Incompatibilities with Postfix 1.1

Postfix 2.0 address classes introduce a few incompatible changes in documented behavior. In order to ease the transitions, new parameters have default values that are backwards compatible.