The Postfix Queue

The Postfix queue manager does the bulk of the work in processing email. Postfix components that accept mail have the ultimate goal of getting the email message to the queue manager. This is done through the cleanup daemon, which notifies the queue manager when it has placed a new message into the incoming mail queue. Once the queue manager has a new message, it uses trivial-rewrite to determine the routing information: the transport method to use, the next host for delivery, and the recipient's address.

The queue manager maintains four different queues: incoming, active, deferred, and corrupt. After the initial cleanup steps, the incoming queue is the first stop for new messages. Assuming system resources are available, the queue manager then moves the message into the active queue, and calls on one of the delivery agents to deliver it. Messages that cannot be delivered are moved into the deferred queue.

The queue manager also has the responsibility of working with the bounce and defer daemons to generate delivery status reports for problem messages to be sent back to the sender, or possibly the system administrator, or both. In addition to the message queue directories, the Postfix spool directory contains bounce and defer directories. These directories contain status information about why a particular message is delayed or undeliverable. The bounce and defer daemons use the information stored in these directories to generate their notifications. See Chapter 5 for more detailed information on how the queue manager works.



Postfix Architecture

General Configuration and Administration

Queue Management

Email and DNS

Local Delivery and POP/IMAP

Hosting Multiple Domains

Mail Relaying

Mailing Lists

Blocking Unsolicited Bulk Email

SASL Authentication

Transport Layer Security

Content Filtering

External Databases

Appendix A. Configuration Parameters

Appendix B. Postfix Commands

Appendix C. Compiling and Installing Postfix

Appendix D. Frequently Asked Questions

Postfix(c) The Definitive Guide
Postfix: The Definitive Guide
ISBN: 0596002122
EAN: 2147483647
Year: 2006
Pages: 130
Authors: Kyle Dent D. © 2008-2020.
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