Limit private messages to contacts and members of the staff

[clarentbloodarthur]

Would it be possible to make it so a simple user can no longer receive private messages by other, random users and only get them from trusted members and/or members of the staff, please? I'm receiving unsolicited sell+illegal shares requests, would like to put a stop to those, like I was able to in the past (I remember being able to disable private messages on the forum shortly after registering).