I'd like to call myself the crazy email guy and for good reasons, I've been an email app nuts from the very start. I've followed various email release, new app, new features and I've tried at this point hundreds.
Mailbox was one of the top 10 email clients I liked and used. I'm very sad to hear that Dropbox will be dropping it. I understand that they didn't get the traction that they were looking for when they moved to provide a business class of services. It was supposed to be the be all of email client and it didn't go that way.
This isn't the only that has suffered this way, many other apps on the market have come and gone. I'm hopeful to see other fabulous email apps and definitely looking forward to see something that will WOW the email industry.