Internal mail database error - Can't delete!

I just faction changed on Outland from Alliance to Horde, and i was on my way to migrate back to Al'Akir. But, as i faction changed i had some new mails in mailbox - Some pets and a Violet Drake from the World Events Achievement.

First off it's kinda weird that the mails even appeared in my mailbox as i already had them all. Now to my problem, when i try to delete the mail this error pops up : Internal mail database error.

I have tried, deleting my WTF / Cache and Interface folders and restarting afterwards. I have tried rebooting my PC several times, i have tried force shutting down WoW and then logging back in but nothing seems to be working. So now i require aid from the big guys!

Also, i would be really glad if i could get some kind of assistance soon-ish as i want to migrate back to Al'Akir as soon as possible.

/ Regards