Mail queues management with Postfix (1.x)

This article was first written in August 2004 for the BeezNest technical
website (http://glasnost.beeznest.org/articles/148).
This article describes commonly used commands in mail queues management with Postfix 1.x. It probably applies for posterior versions, but has not been tested. To show the message summaries in the current queue:
$ mailq
To flush the queue (i.e. force delivery):
$ postqueue -f