Rspamd is an advanced spam filtering system that allows evaluation of messages by a number of rules including regular expressions, statistical analysis and custom services such as URL black lists. Each message is analysed by Rspamd and given a spam score.

According to this spam score and the user’s settings Rspamd recommends an action for the MTA to apply to the message: for example, to pass, to reject or to add a header. Rspamd is designed to process hundreds of messages per second simultaneously and has a number of features available.