Hello, we have a client running exchange 2007 on an SBS 2008 server. This morning they changed ISP's. We have configured our firewall to use the new IP, netowork information. We are able to receive email, access OWA externally, access VPN and browse the internet fine. However, when we attempt to send mail, the mail queues up with the following error:
4126.96.36.199 Primary target IP address responded with "4188.8.131.52. Unable to connect." Attempted failover to alternate host, but that did not succeed. Either there are no alternate hosts or delivery failed to all alternate hosts."
We've already checked with the ISP and they tell us that there are no firewalls on their new modem. We've also verified our firewall - although the outgoing poilcy for email is still there and doesn't need to be changed. Also the MX records are correct and we don't have an SPF record. What could be causing this?