Mailbox Error

[Diametra]

Before ya do a clean install, try tossing out WDB and WTF first. who knows, refreshing the game data and losing any addon settings might do the trick.

[Sweetiepuff]

I had this exact problem with sending mail, as well as the "empty" Friends List.

I realized what was causing the error - Unknown Friend. This is someone who has deleted their character. We have to manually delete this person on Nost (whereas Blizz servers recognize the deletion and automatically remove deleted friend).

I was going crazy for a few hours trying to solve this mystery! LoL