So I had been running iOS7 GM happily since it was released, with Mailbox syncing two accounts. Halfway through the day, I realized that I hadn't received any email, so I opened Mailbox to check my mail and was greeted with this screen.
Needless to say it was mildly annoying. I have since turned on notifications in the default Mail.app (already had the accounts configured) and got rid of Mailbox. It wasn't that big of a deal, but I just don't want to worry about this happening again.
Has this happened to anyone else?