Cannot Faction Change...

So I go into my faction change screen. I drop to my realm, select the character I want to move, and alas I get the error that I cannot faction changed while mail is in or en route to my mailbox. However, I have not sent mail from or to that character recently, at all.

Is there a way I can get this removed somehow in-game? Or am I going to have to wait out a potentially multi-week process in waiting for whatever stupid item was sent to or from my character to make its way back to me?