We have had some issues with losing internet connection once in a while. Normally that would mean our mail server is unreachable and incoming email is bouncing. We've set up MX Backup (second MX record after ours) and while for some providers it was enough (gmail dropped to second MX and was able to queue up mail), others still bounced the email (hotmail).
Is there anything we can do to make sure that we never lose email? We would like to host email internally because there is a lot of internal email traffic. We are also considering a backup internet connection (what would be the proper dns/mx setup for that)? Still even with backup we sometimes lose power so having email queued outside would be perfect but backup MX doesn't seem to be reliable enough.
Please let me know what's possible in our situation to improve email reliability.