The problem is, Inbox already has a BUNCH of VC's behind it. Which means a lot of people only worried about making money on the board. Unless the founders collectively agree they won't sell the company and also have a majority of shares in the company, the first big tech company that comes knocking with an offer will treated like the second coming.
First of all JOBS act Title 3 lets you do crowdfunding. And meanwhile there are old school alternatives:
Banks (older school than VC)
Actual profits (probably even older school)
Broker dealers (crowdfunding before there was crowdfunding)