Add Privacy setting: No contact from large joint servers

Joining bigger servers increases the number of people who can contact you.

Lately, my friends and I get a ton of spam/phishing messages asking whether we would "sell our account" and other things. This isn't good.

Could we get a setting to disallow direct contacts from joint servers if the server has more than x users (100?/250?).
Alternatively, toggling "Allow direct contacts from this Server" on a per Server setting would do too.

Thanks!