For email hosting I use zoho.com which offers a free tier for one domain and $36/year for more domains and features. I've been using them for a few months with one of my side projects (onewaybits.com) and recently started another project with another domain and decided to jump to the paid tier because I had such a good experience with their free tier.
I also use zoho for my personal mail (for about a year so far), and I've also had a good experience.
I'll definitely consider it for a larger project. After Google closed the free tier of the Apps for Business service, I think they are the way to go for side projects :) (which will hopefully convert to paid if they do well!)
zoho.com looks nice. But it only gives 20 accounts on the free tier. Windows live domains, on the other hand, doesn't seem to have a limit on the number of accounts.
