According to an unnamed source, the two products are being eliminated because “growth has not been as significant as expected.” The information available points to Carousel closing down as of March 31st with Dropbox helping users move any photos stored there back to the main Dropbox service. Mailbox will shutdown on February 26th and Dropbox appears to be ready to help clients identify other email clients.
Mailbox was acquired by Dropbox as recently as 2013 and was part of move by Dropbox to expand their footprint of available services. However, competition has been fierce, especially from Google which has been stepping up their efforts with changes to their main Gmail platform as well as the introduction of Inbox. Likewise, Google has been making some pretty significant improvements to its Photos service to make it more of a photo-sharing service. This appears to be forcing Dropbox to make moves to focus more on their primary business and how to keep it healthy, including a stronger push into the enterprise market.