Mail-in-a-Box is a free and open-source program for mail server hosting developed by Joshua Tauberer.
[1][2] The software's goal is to enable any user to turn a cloud system into a mail server in a few hours.
[4][5] The default configuration provides a spam detection system, monitoring, reporting and backup mechanisms.
[6] It can also set up and automatically renew a Let's Encrypt certificate, as well as configuring the detailed DNS configurations needed to ensure that a mail server's IP address is trusted by other servers, and less likely to be blacklisted.
[7] First developed in 2013 by Tauberer, the tool is written in Python.