Singlefin’s three Enterprise Filters (Email, Web and Instant Message) are available with no restrictions for an unlimited time to companies with 10 users or less. You can:

* Filter all spam and block all viruses
* Allow admin and user-level spam quarantines
* Block all web-based porn and (if necessary) eBay or ESPN
* Trigger disclaimers to users
* Launch rules violation notifications to anyone in the company
* Capture and archive 100% of conversations on AIM, MSN or Yahoo! Messengers plus much, much more.

http://www.singlefin.net/free_services.php