"Clear Mailbox" Error Preventing Transfer


I’m hoping to transfer one of my character (Stromcrow - Sulfuras server), but keep getting an error that prompts me to clear my mailbox. The problem is, I don’t have any mail in my mailbox. I looked on the auction house, and don’t seem to have any pending auctions either.

Not sure how I can go about proceeding with a character transfer?

Theres a mail Purge thread for this kinda thing if u scroll down a bit and post there.