Postfix Bottleneck Analysis

Purpose of this document

This document describes the qshape(1) program which helps the administrator understand the Postfix queue message distribution sorted by time and by sender or recipient domain. qshape(1) is bundled with the Postfix 2.1 source under the "auxiliary" directory.

In order to understand the output of qshape(1), it useful to understand the various Postfix queues. To this end the role of each Postfix queue directory is described briefly in the "Background info: Postfix queue directories" section near the end of this document.

This document covers the following topics:

• Introducing the qshape tool
• Trouble shooting with qshape
• Example 1: Healthy queue
• Example 2: Deferred queue full of dictionary attack bounces
• Example 3: Congestion in the active queue
• Example 4: High volume destination backlog
• Background info: Postfix queue directories
  • The "maildrop" queue
  • The "hold" queue
  • The "incoming" queue
  • The "active" queue
  • The "deferred" queue
• Credits