My company (@abc.com) is in the process of merging its operation with another one (@xyz.com) and both are Microsoft shops with Exchange 2010 SP3. The 2 networks are linked by an IPSEC tunnel.
We set up DNS conditional forwarding on each side. In @abc.com network, we conditionally forward all DNS @xyz.com hostname request to @xyz.com internal DNS Server In @xyz.com network, we conditionally forward all DNS @abc.com hostname request to @abc.com internal DNS Server
We then allow TCP/UDP 53 to flow through the IPSEC tunnel.
After that, we found out that in @abc.com, when we try to send email to [email protected], the emails are all stuck in the queue viewer of the Edge server with no error code.
1) In @abc.com, I went to the Edge server, in EMC / Edge Transport / Properties / External DNS Lookups, the DNS servers are all valid external DNS servers. I did NSLOOKUP on the Edge server and was able to resolve external @xyz.com nicely.
2) I turned on verbose for Protocol Logging of the Send Connectors but the SMTPSend file does not record anything stuck in the queue.
3) I have a feeling that the Edge Server disregards the External DNS lookups and go straight to the conditional forwarder to get this the internal MX record of @xyz.com instead. Because internally @xyz does not have any MX record and so it was therefore stuck in the queue.
Any thoughts?
Hi,
To satisfy your requirement, I suggest you that create a forest trust between xyz.com and abc.com and then create cross-forest send connectors.
More details about how to configure forest trust and cross-forest send connectors: Create a one-way,outgoing,forest trust & Configure a cross-forest Send connector
Best regards,
Ivan Wang
Please refer to the link below for the solution
https://social.technet.microsoft.com/Forums/exchange/en-US/2b34183b-5069-4959-8bac-4e5ef05d32f6/dns-conditional-forwarding-and-email-stuck-in-queue-viewer?forum=exchange2010#e26d774d-7343-4fb2-92f1-37db3ecc4bf6