MyBB Community Forums

I literally cannot find a plugin that blocks users from Private messaging until they post a certain amount of times. Well I can, but they are outdated

A plugin may well be less work in the end, but not essential IMO.  You can use Group Promotions to promote - for example - Registered users.  Don't allow that group to use PM's.  Using post count, promote them to another user group which can. 

cheers...