I recently changed our ISP from Verizon DSL to a Towerstream T1 and now I have some emails/domains being held in the Exchange System Manager Queue. I updated the IP that is hosting our domains so that isn't the cauise and did Reverse DNS entries on Towerstreams end for our domain. The only thing that has changed is that I removed the smart host address on the Exchange server since Towerstream serves doesn't require one.
Any ideas of why these aren't getting delivered???