12 mtasim — a testing tool

The mtasim utility is a MTA simulator for testing mailfromd filter scripts. By default it operates in stdio mode, similar to that of sendmail -bs. In this mode it reads SMTP commands from standard input and sends its responses to the standard output. There is also another mode, called daemon, where mtasim opens a TCP socket and listens on it much like any MTA does. In both modes no actual delivery is performed, the tool only simulates the actions an MTA would do and responses it would give.

This tool is derived from the program mta, which I wrote for GNU Anubis test suite.