Dropbox just delivered some bad news for Mailbox users.<br />The company will shut down its popular email app along with its its photo storage app Carousel, Dropbox announced Monday.<br />Though neither app has a clear replacement, the company says it will bring some of Carousel's "key features" to the Dropbox app .<br />Mailbox was already hugely popular when Dropbox acquired it in 2013, but had been struggling to deal will the massive influx of users.<br />The app is often credited for introducing gesture-based controls to email, allowing you to organize messages by swiping right or left, a design that has been imitated by dozens of email apps since.