Posted 15 May 2011 - 01:54 PM
It's also possible to read PM's directly out of the database, if you have access to phpMyAdmin. I wouldn't read PM's if I didn't have a very good reason to, though - they are supposed to be private, after all. If any of your members ever find out that you're doing it, don't expect them to take it lightly. If you're going to read messages, you may want to add a disclosure note on your site mentioning that admins have access to them. That way, you can prevent compromising your users' trust.
IPB has a feature which allows members to report offensive or rule-breaking PM's to the moderation team, and you may want to consider how useful that would be to you. Of course, you have to depend on your members being responsible enough to use it.