Mailbox's latest update (1.1.0) broke the app for jailbroken devices. It will not let you authorize a new account - it will give you an error every time. The developers are aware and when asked, have so far not replied as to weather or not they will fix this. EDIT: This was their reply to someone else - "It's likely because of the latest update - it's caused crashing with jailbroken phones. Unfortunately we don't support them". Doesn't sound promising.