This should be a standard user mode at this point. It prevents spam while still allowing notice of legit messages.
Ignores private messages from unknown users. Instead, you will be told that someone is attempting to message you, and the user will be informed that you have this mode set. You can choose to receive messages with the /accept command, but will not receive any previous messages. Messaging a user automatically accepts them. Messages from unidentified users will still be blocked by +R
This should be a standard user mode at this point. It prevents spam while still allowing notice of legit messages.