1. Patching qmail
Contents
https://notes.sagredo.eu/files/qmail/patches/
https://notes.sagredo.eu/en/qmail-notes-185/patching-qmail-82.html
http://qmail-spp.sourceforge.net http://qmail-spp.sourceforge.net/doc/
QREGEX (v2) 20060423 - README April 23, 2006 A Regular Expression matching patch for qmail 1.03 and netqmail https://github.com/c-rack/qmail/blob/master/README.qregex
1.1. qmail-spp
Author: Pawel Foremski Version: 0.42 More info here qmail-spp provides plug-in support for qmail-smtpd. It allows you to write external programs and use them to check SMTP command argument validity. The plug-in can trigger several actions, like denying a command with an error message, logging data, adding a header and much more. The qmail-spp functionality is disabled by default, so that it will be transparent for ancient users of this patch. If you want to enable qmail-spp just export the variable ENABLE_SPP in your run file. Note that the variable NOSPP is not available in this combined patch.