16.5 Tuning to Deal with Spam

The vast amount of spam sent from forged return addresses to nonexistent recipients causes correspondingly vast numbers of bounces and doublebounces when qmail bounces the spam and finds that it can't deliver the bounce to the nonexistent return address. Because nearly all doublebounces are now due to spam, there's little point in doing anything with them. To throw them away, change the configuration file doublebounceto to nobody, and if you haven't already done so, create ~alias/.qmail-nobody containing a single comment line to throw the mail away. (The file can't be empty, because that's treated as a default delivery, but just # will do.)

This still queues and delivers doublebounces. To throw them away without queueing them, apply the small patch at http://www.qmail.org/doublebounce-trim.patch, which adds a special case to qmail-send so that if doublebounceto contains a blank line, doublebounces are just discarded.