Managing multiple Postfix instances on a single host

With postfix 2.6 or above, you can manage multiple SMTP service on the same machine.
This is a cool feature that allows you to separate different SMTP services behavior on the same machine.

Postfix is a general-purpose mail system that can be configured to serve a variety of needs.
Examples of Postfix applications are:

  • Local mail submission for shell users and system processes.
  • Incoming (MX host) email from the Internet.
  • Outbound mail relay for a corporate network.
  • Authenticated submission for roaming users.
  • Before/after content-filter mail.

A single Postfix configuration can provide many or all of these services, but a complex interplay of settings may be required. In this section we take the view that multiple Postfix instances may be a simpler way to configure a multi-function Postfix system.
With multiple Postfix instances, each instance has its own directories for configuration, queue and data files, but it shares all Postfix program and documentation files with other instances.