[How To?] suspected spammer can ONLY send PMs to admins/mods?

[Der Meister]

If I have a person on my board who I don't want PMing any of my users, but who I would like to hear from myself, how do I do that?

In other words I don't want this person spamming anybody, but I want him to be able to answer the PM I sent him asking him a few questions.

[.m.]

not sure if such modification exists
however, PMs can be disabled for newly registered users (or specific groups) and there can be a private section
in which the posts are visible only to the thread starter and your forum staff (or specific user groups)

see the details here => Make post only visible for admin and individual user