If you want to replace Google Apps because of price or because of privacy there are actually tons of good choices these days. I reconciled several services and servers on Bluehost recently saving a considerable amount of money. There was a quirk that meant I couldn’t FTP at first but a quick call to tech support fixed it. And, unlike Google, there actually is tech support and they answer their phones quickly. The price is right as well at only $3.95/mo for the low tier. I paid the extra for the pro version. But that’s only $19.99/mo — less than what Google chargers per user.
I have several different hosts running on it. They’re all low volume — mostly different companies. I have a lot of archived email though. Nearly 4 gig, which was why I had been hesitant moving. However Bluehost handles it no trouble. This blog is running on it too.
About the only quibble is that by default there’s no CalDAV or CardDAV server. Personally I hate having too many of those. iCloud is enough for me and then I do one directional sync to Google Contacts via Contacts Sync for Google Gmail. I do that so I can actually find addresses quickly in Google Maps. But I do it one way so nothing gets screwed up by Google. However if you really need calendars or contacts in the cloud I was able to install Baikal in about 10 minutes just using FTP. Much easier than the OSX Server solution I’ve heard some propose.