Thanks for all your help. The problem is: My friend can't get PM ID# which include his bitcoin address.
My friend did send PMs including his bitcoin address, but it happened three years ago.
Since he can't access his account now, how can he find the PM ID#?
He checked his related email box, but can't find any (maybe deleted)
All he can remember is during which month he sent these PMs. Is that kinda of proof?