[robcomputerguy]

Are you asking because someone told you it could be? Dropbox can share a static, html website, not actually be a computing machine that could run software apps like an email server.

If your question comes from a certain idea about how you might possibly do that, by all means reply and I'll see if I can explain further.

[fakeer]

It was just a subjective question. I thought Dropbox could just extend this functionality.

Or maybe 3rd party apps/services could felicitate this just the way e.g. http://calepin.co does for static site generation. Use Dropbox for storage of emails. And naturally you'll have a local email archive on all your connected devices.

So, seems there's nth like this as Dropbox doesn't let us to do the compounding, as you also pointed out.