My MX record for my domain points to IP of a smarthost in our DMZ that scans e-mail before delivering to our internal Exchange servers.
Since I will be putting a new/different smarthost up with a different IP, I will need to update the MX record to point to the new device.
Does anyone know how long that usually takes?
Since I can't keep the same IP for the new appliance (due to restructuring of our subnets), is there a way to make the process go quicker?
Or should we just expect downtime for e-mail for an hour or so?