Postfix - the Big Picture

Note: this web page is no longer maintained. It exists only to avoid breaking links in web pages that describe earlier versions of the Postfix mail system.

The figure shows the main Postfix system components, and the main information flows between them. Postfix system components are introduced in the Postfix anatomy documentation.

• Yellow ellipsoids are mail programs.
• Yellow boxes are mail queues or files.
• Blue boxes are lookup tables.
• Programs in the large box run under control by the Postfix resident master daemon.
• Data in the large box is property of the Postfix mail system.

• The Postfix command-line utilities.
• The Postfix resident master daemon.
• The DNS lookups by the SMTP server and client daemons
• The bounce or defer daemon and the flow of bounced mail.
• The address rewriting and resolving requests by the SMTP server and by the local delivery agent.
• The flow of mail forwarded by the local delivery agent.
• The flow of postmaster notices for protocol errors, policy violations, etc.
• Triggers to alert the pickup daemon and queue manager that new mail has arrived in the maildrop and incoming queues, respectively.