Описание тега qmail
Message/mail transfer agent designed for UNIX hosts.
Qmail is a public-domain mail transfer agent for UNIX hosts written by Dan Bernstein.
Useful links:
Tag usage
The tag qmail can be used for all programming related problems. The tag can also be used for setting up a simple mail server. Please note that https://serverfault.com/ is another Stack Exchange website where you can ask especially configuration specific problems.