pop3spam is a POP3 client which connects to a POP3 server and deletes unsolicited mail.
Eventually your normal mail-retrieval utility (e.g. fetchmail) can gather all (cleaned) mail as usual. The program is intended for people with low bandwidth. It's very annoying if you first have to download lots of large messages just for the sole purpose of deleting them afterwards because your local spam filter debunked them as spam. It's also annoying to download very large messages (attachments) at all.
pop3spam doesn't use any hard wired regular expressions so it should basically work with any recent version. For information about the configuration and use of pop3spam, take a look at the man pages pop3spam(1) and pop3spamrc(5). A sample configuration file exists in the directory doc/ in the source tree.