If the intended recipient has a valid e-mail address associated with his/her account, s/he'll receive an e-mail stating that someone tried to send a PM but the intended recipient's mailbox was full. That (sort of) solves half the problem.
If the intended recipient has a valid e-mail address associated with his/her account, s/he'll receive an e-mail stating that someone tried to send a PM but the intended recipient's mailbox was full. That (sort of) solves half the problem.