Exchange Migration Outbound Email

[ITGURU]

I've got to the final point of an Exchange 2013 to 2016 migration.

However, I have an issue with outbound email.

 

I cannot redirect email to the new internal server IP as I don't have access to firewall, so currently I have inbound mail going to the old server which still reaches the mailboxes on the new 2016 server and sending external emails still go out via the old 2013 server.

 

I can add a second Network connection (or add the IP as a second IP) to the new 2016 server assign it the same IP (obviously after shutting down the 2013 server) and I can then receive external mail without any issues, it all delivers fine.

 

However, any external emails send don't go and get stuck in the queue.

In the send connector I removed the 2013 server and added the 2016 one.

 

However, if I then revert the changes, bringing the old 2013 server back online with the IP all the delayed emails then send.

 

What have I missed and is there a way to force which interface IP the email is sent out on as I suspect that may be the issue?

[sister_annex]

are you sending through a smart host?

[ITGURU]

are you sending through a smart host?

 

Yes I am. external provider