My apologies if the answer is obvious, but why does he mention Mailbox?
What is Mailbox (from wikipedia):
Weeks before its launch, pre-registration prompted a wait
list of over 380,000. Mailbox was added to the iOS App Store
on Thursday, February 7, 2013; it became the second most
downloaded free app in the App Store that day
In March 2013, Mailbox was acquired by Dropbox Inc.
So: they hyped up their app, and were able to exit less than a month after launch.