Shared namespace between Exchange 2013 & 2010 with internal relay not working

Hello Technet,

I hope someone can help me with my current issue. I am currently trying to setup a shared namespace between two separate Exchange organizations one is Exchange 2013 while the other is Exchange 2010. Exchange 2013 is patched to CU10 while 2010 is running SP3 rollup 7 both are located in separate domains on different networks. Now all of the steps online seem to be pretty strait forward.

I setup the namespace to be shared on both Exchange systems and set the type to “internal relay”. I then setup a send connector on Exchange 2013 as internal and pointed it to the Exchange 2010 server. And setup a receive connector on Exchange 2010 to allow the incoming connection. The namespace to be shared is the default domain on the Exchange 2010 server but it was switched to “internal relay” as well. Now when attempting to send a test message from Exchange 2013 to an email address that should be valid in Exchange 2010 because it does not exist in 2013. The message appears to be discard by Exchange 2013.

It does not appear from the message tracking logs like at any time does Exchange 2013 even attempt to use the send connector to transfer the message over to Exchange 2010 where it should be valid. More over when looking at the queue viewer I see no entry appearing for the send connector showing it even tired sending the message over.