We all get a mailbox from marleybone, as we do the post office quest. Why not have mailbox we can use?
There could be a button much like the 'add to a group' on a wizard's profile that says, 'send care package'. And that the button could only be used inside the Marleybone post office.
I've often found myself wanting to help another wizard with a robe, ring, or other similar object that my own wizard can not utilize. There could be a limit of sending 2 per day; and that it could only be to someone on your friends' list.
We could 'check the mail' anytime we walk up to our mailbox, whether it be in a dorm, fantasy mansion or other house. The wizard that you mail something to, may play at a different hour than you do... making it a nice surprise for when they do come into the game.
And for lower levels, they would have to actually make it to marleybone & do the quest before getting their usable mailbox. And lets face it, by the time you get to marleybone, you can get your own goodies and loot - making it less of a beggar's tool to use.