Feature request: Restrict new user PM's

I'd like to have a preference to restrict new user PM's to a configurable number or amount of time between messages. This would be to prevent new users from flooding and/or spamming the system.

Also, in the event that a spammer is found, ban the user from the mail system and warn them. Perhaps even delete all messages from that user.

You can already specify a time period to prevent flooding.

And you can also ban a user from the PM system (disable the account in the user settings).

Yes I understand both. I'm saying that an "evaluation" or "probation" period for new users would help with spammers.