assblocker blocks IPv4 addresses of assholes at the local firewall by
manual use and automatically by monitoring mail log files. Does not
support the shitshow that are IPv6 addresses, which you shouldn't be
allowing on mail servers anyway, due to the shitshow of trying to get IPv6
e-mail into the e-mail shitshow known as Google Inc.
Concept and Theory of operation:
Allows blocking and unblocking of specified IP addresses given on the command-line. This is not terribly useful by itself. Assblocker also however, monitors the mail server logfile for degenerate assholes who need to be blocked either temporarily or permanently, Assholes attempting to break into e-mail accounts are blocked temporarily for a specified number of days (30 by default). Assholes attempting to probe your mail server for vulnerabilities are blocked permanently. Unfortunately, these are only blockable by name, so this functionality only works with blackhat support services masquerading as either research projects or commercial "intelligence" and "identification" services.
You can ask for help with assblocker on the mailing list.