Re:Not sure you're getting it (Score 2, Informative)

Sure! These are things you can do if you are using Postfix as your MTA.

In your main.cf file include this at the bottom

body_checks = regexp:/etc/postfix/spammerbodies

Learn more here about main.cf and other cool spam protections here:
http://www.afp548.com/Articles/mail/spam2.html including a really great RBL configuration.

Create a spammerbodies file and include this line
# various encoded URL formats. if they're trying to disguise the URL then they're up to no good /(ftp|https?):\/\/([^\/]*@)?([01]{10,})?(\d+|00+\d +(\.00+\d+){3}|[\%0-9a-zA-Z\.\?_-]*\%[\%0-9a-zA-Z\ .\?_-]+)(:\d+)?(\/|"|\s|$)/ REJECT

You can get a full list of other scripts here:
http://www.securitysage.com/guides/postfix_uce_bod y.html

and here

http://www.hispalinux.es/~data/postfix/

Hope that helps.