I can't delete a folder in my mailbox.

I have tried to delete it on my ipad, ipod, iphone and computer, none will work. There's no emails in it, and if I do delete it, the next time I sign it it's back. Same thing happens if I try to rename the folder, it switches back after I sign in again. I can't find anything online about this and I have no idea how to fix it. Please help!!!