Everyone.net's "Sponsored Mail" seems to offer everything I want, but I don't want to subject my visitors to tons of pop-up ads. Worse, it has constant popups to install ActiveX programs and other spyware. Ads are fine, but not popups.
I simply would like to provide free email to visitors. I'm looking for a free or low-cost alternative. I prefer outsourcing rather than hosting it myself to avoid problems with spam and abuse.
Have you looked at Hivemail? Everyone.net also has group mail that doesn't have the pop ups or ads. You can put your own banner ads in if you want. I use group mail on one of my sites. I think it's $10-15/month per 100 accounts and there may be bulk discounts.