Hi,
The article you read mentions that CBR might be necessary in certain scenarios to avoid routing issues between Exchange Online (EOL) and Exchange On-Premises (EOP). CBR, also known as Conditional Mail Routing, is designed to route mail matching certain criteria through a specific outbound connector. If your setup involves complex routing requirements, implementing CBR could help manage these scenarios effectively. Based on my personal experience, it is suggested that not using CBR.
CMT routes emails by using its own connectors. It ensures that all messages from Exchange Online mailboxes are routed through Exchange On-Premises before being delivered to the Internet, and incoming Internet messages are routed through Exchange On-Premises before being delivered to an Exchange Online recipient. This setup helps maintain compliance and control over email flow.
It is recommended to use a third-party certificate with the A record name of the mail server. This ensures secure communication between servers. One potential gotcha is ensuring that the certificate is correctly configured and trusted by all involved parties to avoid any disruptions in mail flow.
Please feel free to contact me for any updates. And if this helps, don't forget to mark it as an answer!