If you enable Spam Assasin it will block most spam from reaching your e-mail.
SpamAssassin is a computer program
released under the Apache License 2.0 used for e-mail spam filtering based on
content-matching rules. It is now part of the Apache Foundation.
SpamAssassin uses a variety of spam-detection techniques, that includes
DNS-based and checksum-based spam detection, Bayesian filtering, external
programs, blacklists and online databases.
The program can be integrated with the mail server to automatically filter all
mail for a site. It can also be run by individual users on their own mailbox and
integrates with several mail programs. SpamAssassin is highly configurable; if
used as a system-wide filter it can still be configured to support per-user
preferences.
SpamAssassin was awarded the Linux New Media Award 2006 as the 'Best Linux-based
Anti-spam Solution'.