I don't agree with SM not being able to add a domain, unless the MX record points to it.
We use MX records priority like this:
MX 10 - Front-end gateway #1
MX 20 - Front-end gateway #2
MX 30 - BackUp gateway
MX 50 SMail
Gateways #1 and #2 move mail to SMail, after they have done their own filtering et al.
These gateways ... as it stands right now, DO NOT know anything specific about SM
other then that just happens to be the IP address that they move the email to, after filtering.
If you do an MX check in SM... it always says the MX does not point to it...
How do you get around that - the above rule was in place??