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ScotchTech-5160 asked LucasLiu-MSFT commented

How to split 443 traffic between 365 and cloud proxy?

We have an Exchange Hybrid recently setup. We have a conditional access rule which will trigger depending on the source IP of an Outlook client. The issue is that our default route for 443 (which Outlook uses) is to route everything via a cloud proxy called Zscaler, but we want to exclude and bypass the cloud proxy for anything that Outlook routes to behind the scenes. There are many exclusions recommended by MS, and a lot that contain wild card URL's, however firewall routes don't allow wildcards, and also 365 sites are always changing.

Any suggestions?

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Hi @ScotchTech-5160 ,
Based on my knowledge and research, the port through which the service required by Outlook passes is determined by the design and cannot be changed. According to your description, you deployed a third-party tool to proxy the routing of port 443. If you want to exclude Outlook-related routing, you can only set it through your third-party software. Microsoft is unable to make changes, so limited help can be provided. Regarding the URL and IP required by O365 you mentioned, these are also provided by the design. We cannot make changes.

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