Mail is a good service to host yourself. With a couple of digital ocean boxes you are golden. Set up your backup MX to just hold mail and deliver it to your primary MX.
SMTP is forgiving and you can have many hours of outage of a primary mail server without losing mail.
I wish I did. Personally I'm very much in the Google ecosystem, and this has been a repeat point of friction. Thus far the approach has been to go on site with a trusted intermediary that has the required infrastructure, but it's not sustainable.
Not much scares me technically like the idea of ineptly deploying a mailserver.
Zarafa is excellent (and works with MS Outlook if you need that).
Edit (to elaborate more): it's open source, has a very nice web ui, supports pop/imap/outlook, does activesync and mobile push, uses other standard opensource software (postfix, mysql), is easy to backup, comes with good documentation, is simple enough to get up and running (there are pre-built deb and rpm packages), integrates with LDAP and you can get a paid support contract if you need/want one. Their open source site is here: https://community.zarafa.com/
I'm not affiliated with them - just a happy sysadmin whose managed lots of Zarafa installs in the past.
