Qmail-spp enables plug-in functionality for the qmail SMTP application, enhancing its capabilities.
The development of qmail-spp was started due to the lack of a common way for enhancing qmail-smtpd's functionality using patches that are often incompatible with each other and require recompilation. Additionally, qmail-spp offers the flexibility of enhancing your mail server with any language of your choice, allowing you to easily integrate it with other software.
Plugins are extremely useful external programs that execute after SMTP command processing, but before acceptance by qmail. This lets you add extra checks on arguments before accepting them, such as checking the envelope recipient address against your "black list". The best part is that plugins can be written in any programming language, making them completely flexible and independent programs.
When writing plugins, keep in mind a few rules: they should not read anything from standard input, should not exit with error code 120, should print all errors to standard error (in order to be logged), and can print commands on standard output.
Overall, qmail-spp is a must-have software for anyone looking to enhance the functionality of their qmail-smtpd. It's easy to integrate and has the ability to improve your mail server's security and reliability.
Version 0.42: N/A