The managed file transfer sector is hot and there is no winner yet. Even a YC company called WireOver [1] is working in this space.

A little bit precient, my company developed a free Outlook add-on to send dropbox files as attachments [2] in 2012.

- [1] http://www.wireover.com/

- [2] http://blog.nektra.com/main/2012/05/23/integrating-dropbox-w...