Disable to send EMail with Forum-System for Users lower than Admin
Disable activation of this function for each user by removing option out of "Register Page" and "Profile Edit Page". -> no one is able to activate this feature -> if no one is able to activate this feature, no one is able to use it (only admins are still able to use it globaly)
drawback: people who enabled "Allow users to email you?" before this mod is installed, can not change this feature anymore. Mod needs to be disabled to change this option in profile.