I see a lot of people saying that apps die when they get acquired. Whilst this is technically true, it’s shortsighted reasoning. Mailbox had no guarantee of surviving on its own, it was a free app based on other companies’ email services with no revenue model. Mailbox could have died even sooner if Dropbox hadn’t bought them. I don’t know this for sure, it’s a possibility, but Mailbox might have decided to be acquired only because they knew the outlook for sustainability was bleak.
By the way, Eddy Cue’s son worked on Mailbox. Is he now working for one of Apple’s largest iCloud competitors?