From the forums FAQ:
Dealing with Troublesome Users
Can I block posts, emails and messages from specific users?
If there are particular members that bother you and you do not want to see their posts or receive Private Messages and Emails from them, then you can add these members to your 'Ignore List'. There are several ways to do this:
Through your User Control Panel: User CP, Settings & Options, Edit Ignore List. Then, type their name into the empty text box and click 'Okay'.
