Earlier quoted context omitted.
That's hardly a reason to not open-source. You're not required to provide support just because you release your source code. Even a dump of their repositories would be useful for people who are interested in Mailbox.
No; but often the server components are heavily tied to some other proprietary libraries that they're not ready to open source. They could remove all proprietary code from their codebase, but that costs money - likely more than they were willing to spend on this product. Unless open source is part of your marketing strategy (which means the effort would have a budget), it's really difficult to open source an existing…
Nobody asked them to support it, or whatever. Just dump the damn thing online so others can pick up and continue to "help fight your inbox to zero".
Clearly their intention here was profits and since they didn't see any - they kill it off. They won't do it so nobody else should try to safe email either.
I wanted to get my company (over 3,000 users) off DropBox long time ago after each update comes with new issues. But this just broke camel's back. I will make the switch happen this weekend.