Enable SMTP (or SMTP Profile) to be used as backup MX. It just spools mails and sends it to external mailservers. Would be nice to have a per domain settings how long a mail should remain in spool until it gets sent back and what are the retry intervalls to send to a external host.
Jason Harrison commented
Ok, so we need the time in spool and retry intervals exposed in the UI. I would personally like to see full mail bagging support. Keep all email for x hours or days. That way in case a problem occurs on the inside mail server(s) at least there will be a way to re-lease a bounced message or any email that was not routed during the internal outage. Would add a layer of continuity in the Sophos UTM that I have seen in other UTM products.
Bob Alfson commented
This is how it works now except that the time in spool and retry intervals only can be set at the command line.