I know the privacy thing and i really dont like to view my members PM (and vice versa) but you know how SMF works once a PM is sent, a copy of that message can be also seen at the email notice.
The only people that should be getting the email notices are the people that have requested to get notified via email - when "THEY" themselves get pms from other people. Not when the pms are to someone else. (you cant set it up to where you get notifications on pms that other people send to someone else).
Those notifications via email wont even go out unless that member sets that preference in their profile.