We recently switched moved our exchange environment from a physical box to a vm and upgraded to Exchange 2010 SP3. Following the upgrade and server move we are now unable to send to certain domains. We did not change the DNS record as we simply were going to change the NAT in our asa to point to the new server. We are using office365 as our spam filter and those settings appear to be correct as well. When users send to the affected domains they recieve :
Delivery is delayed to these recipients or groups:
Mike ******* (mike@*************.com)
This message hasn't been delivered yet. Delivery will continue to be attempted.
The server will keep trying to deliver this message for the next 1 days, 19 hours and 52 minutes. You'll be notified if the message can't be delivered by that time.