impaler is correct.
I'll add that if iCloud gained that service today I wouldn't use it due to reports of some "spam" being blocked completely with no knowledge of the end user.
Google Apps is one of the cheapest and easiest to set up. Customer service not great. I have one domain there.
Microsoft's Office 365 (email hosting version...not the application suite version) will give you Exchange for about the same price but is a little more difficult to set up. No customer service to call for small users. I have one domain there.
There are third party companies that also host Exchange, such as Sherweb. They're a bit more expensive but you get real customer service. I've set people up with them so that I won't get a lot of email/Exchange problem calls. They're very helpful.