I'm afraid this answer isn't going to help much... but...
I've had mail forwarded when a contact had changed addresses, but I've also had mail returned to me when a contact's address had changed. I think it depends on who is in the mail room on any given day... I've even had mail returned to me when addressed correctly, marked "addressee unknown." I e-mailed the intended recipient and asked if their address had changed, they assured me it had not, I put the letter in a new envelope and addressed it exactly as before, and they got it that time. So, go figure...
I cannot do everything. I accept that. Not being able to do everything is no excuse for doing nothing. ~ Helen Keller