Postfix - the Big Picture

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.