I would recommend FastMail over other mail services to founders. Its features are fairly comparable to gmail (and presumably windows live mail, though I haven't used it). Additionally, there are some advanced features that seem particularly useful to small companies: the capacity for setting up lots of aliases pointing to multiple destinations, the ability to add super cheap small-storage accounts (good for interns), the ability to share folders, and Sieve filter scripting support all come to mind.

They also have a pretty transparent, non-evil privacy policy. http://blog.fastmail.fm/2013/10/02/updated-privacy-policy/

Plus, you're now supporting a small independent company! http://blog.fastmail.fm/2013/09/25/exciting-news-fastmail-st...

I wrote a blog post about switching from gmail to FastMail that will give you an idea of the service if you haven't seen it before. http://www.maxmasnick.com/2013/07/19/fastmail/