Ask HN: What's The Best Alternative To Google Apps?

What's the best alternative to Google Apps for small businesses? I love gmail, but I'm not keen on creating another G+ account & I'd rather have something that weans me off the Google ecosystem as I'm relatively annoyed at having to opt into all of their services if I just want to use one.

I get that they want us to use everything, but sometimes I just want email. What's the best alternative out there? I figure you guys have some solid opinions.