Update 11/13/2023: We added new information on how to know when this change is released to your organization.
Today, we are announcing an update to our requirements for SMTP relay through Exchange ...
Updated Feb 22, 2024
Version 19.0
Blog Post
Carolyn_Liu
Microsoft
Microsoft>What do you mean by "O365 cannot support IP-address-based connectors from a 3rd party service"? As it does work currently. Am I missing anything?
The on-premises inbound connector was designed for customers to relay emails from their on-premises system. Not meant for 3rd party cloud services to relay emails for their customers. We are working on a plan to address the issue. There are bad actors pretending to be such services. We are working on a plan to throttle emails from shared IPs using Inbound connectors but will offer exceptions for registered 3rd party cloud service providers if they follow the best practice stated in this article. Scenario Integrate Microsoft 365 or Office 365 with an email add-on service | Microsoft Learn.
Feel free to contact me directly (caliu@microsoft.com) if you are interested in the plan. Love to hear the feedback.
>Is the return-path 100% trustable? I'm afraid there could be different scenarios not taken into account. For big service providers, this change could be critical and there should be a 100% trustworthy way to test it out.
I believe it is, as we re-write return-path once the email is accepted. But we will also consider to make this info available to our impacted customers in MessageTrace.