For a long time I thought that when postmaster is full, you lose the most recent things, but apparently it's not... After a long grind in the EAZ, I just lost two exotic engrams, three exotics and 4 last wish keys... I wonder if there is any chance I can get those back... F
Nope. The postmaster is not meant for storage. Anything you want to keep, take it out of there, or you risk losing it.