Hello,
I have a Exchange 2010 and 2013 environment (migrating to 2013) and I've noticed all my internal clients that are on Exchange 2013 send through the Exchange 2013 server onto the 2010, then externally (according to the headers).
I went in and reviewed my Send Connector settings and sure enough my Exchange 2013 server was not part of the SMTP Connector's source server. I went in and added Exchange 2013 and took out 2010 so that all mail is sent through my new server but it does not work, the messages never leave the on premise and are stuck.
Examining the Queue Viewer, there is no error they just sit there.
Once I remove Exchange 2013 from the "Source Server" and leave my Exchange 2010 server in there, it works fine, but mail is going from Outlook Client > Exchange 2013 > Exchange 2010 > External Relay Server (Microsoft EOP / Office 365).
I want to take Exchange 2010 out of this flow to prepare to completely uninstall it after all dependencies for this server are dealt with.
What is the issue? Thank you !!