We have been running Exchange 2007 servers for a number of years. Until this week everything has been running correctly. The only change was one of our CAS/Hub Transport servers was given more RAM and rebooted. Here is our setup.
1 Mailbox Server
2 CAS/HUB Transport Servers
MB Server = Inside network.
CAS1 = DMZ server handles webmail/iPhones etc.
CAS2 = Inside network, has Foreign Connector for FAX servers.
When someone wants to send a fax, they use an email address @1234567890.fax. I believe the standard is for the mailbox server sends round robin to the two CAS servers. What has started happening this week is when a message gets routed to CAS2 from MB the fax works, but if the message goes to CAS1 it tries to send it out the external connector to the Internet, which then fails due to invalid DNS.
We have reinstalled the foreign connector (FAX software.) We have spoken with the FAX software vendor and they claim the problem is with Exchange. We have spoken with Microsoft and they have said we can disable CAS1 from receiving emails inside or install the software on CAS1. The later would require opening up NETBIOS through our firewall. Neither is acceptable especially since it has worked flawlessly for years.
I have researched this on the Internet and have found a couple of things. 1 person said that a send connector should be installed on CAS1, I believe Microsoft tried that, but not sure if they did it correctly. The other person stated that installing in on 1 Hub transport server should allow all the Hub to route messages destine for the Foreign Connector.
What is the correct way it should work and how can I fix it?