We often get request from customers to control mail flow routing in a hybrid deployment, for various compliance requirements. Achieving the desired routing greatly depends on where the MX record is p...
Updated Aug 17, 2022
Version 4.0
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Advanced Office 365 Routing: Locking Down Exchange On-Premises when MX points to Office 365
Arindam_Thokder The above rule would still have issue with UM. When a UM message is left from someone outside of Exchange, Exchange will typically put "CALLER ID NAME <>" as the sender. Exchange would consider the message external (I believe because of the email address) and would redirect it because it doesn't have the aforementioned IPs in the received header