Honestly, these days it's probably easier and cheaper to just buy Google Apps or Office365, but if you want to control your own destiny it's really not difficult.
http://arstechnica.com/information-technology/2014/02/how-to...
- Migrate mails over to SaaS (Gmail, Amazon mail, or Exchange online) .. Probably the best option, unless you want to run your own
- Run a "full featured" open-source mail service like Zimbra on servers on any cloud of your choosing!
- Run a simpler old-school mail solution, like postfix + https://roundcube.net/ for better access
Actually if you need help doing this migration, I'd be happy to help (I'm mostly an Ops person)Free::
http://www.iredmail.org/ ... also has paid version
Paid::
http://www.afterlogic.com/mailsuite/linux-email-server
With each of the options above, you get the complete stack.
::Email server (IMAP + SMTP + POP3)
::Spam protection etc
::Web Client.
And for each of them, you also get a decent web admin panel out of the box.
Trust me, you really don't want to be spending the next week putting the individual components together and getting them to play nice yourself.
• Google Apps.
If no, move to Google or Microsoft.