Centralized Mail Transport (CMT) has been in Exchange Online for a while, and we often see customers using it without even realizing why. Because CMT introduces message routing complexity, increases ...
Updated Mar 31, 2023
Version 5.0
Blog Post
Hi and thank you for that excellent article.
I found this post after having exactly the routing problems that are mentioned.
We have CMT enabled, while most of the mailboxes are still on the onprem hybrid exchange servers in multiple forests. Because of complex Distributionlist setup, we need to move the DLs first to EXO.
Now, if someone from onprem sends to the DL, the mails to the members are going out via MX routing and not via the CMT outbound connector. But this mails are blocked because of spoofing detections at the inbound mailgateways.
As I understand, if we create a 2nd Outbound Connector without CMT, we can route this mails again directly to the onprem Exchange servers, bypassing the MX delivery.
What are possible issues if we use this workaround?
Or is it better to change the inbound Mailgateway configuration to allow this mails coming from EXO?
Any help would be highly appreciated.
kind regards
Peter