Usergroup PM restrictions

[WebSpidey]

Hello,

I run an online community that is based on a limited registration system... In short, people who are invited are granted registered accounts, while any random peopel who register on the site are forced to await validation.

Obviously I need some means to communicate with them if I am not just validating everyone.

Therefore I have granted them their own forum section for "users without validation," where they can create their own threads. None of them seem willing to post any information in a public section though.

I would like to give them access to the PM system, but the last time I did this, it resulted in someone spamming my other members with advertising.

Would it be possible for someone to create a hack that would add new permission fields to all usergroups, where you can set permissions for which usergroups can send PMs to other usergroups?

As an example:
Members awaiting email confirmation and/or account validation could only PM administrative members of the forums.