EDIT 9/19/2023: This blog post has received significant update.
In this second part of the Demystifying Hybrid Free/Busy, we will cover troubleshooting of Hybrid Free/Busy scenarios, more specifica...
Updated Sep 19, 2023
Version 16.0
Blog Post
Mirela_Buru
Thank You, Sorry I forgot to mention, I checked on all Exchange Servers, they're doing out to the Internet directly i.e. internetwebproxy is empty on all. We don't have internet access on any Exchange Server but Hybrid Server can make outbound requests to anywhere on port 80, 443. I checked all URLs are accessible on Hybrid Server. Free / Busy was fine previously with the same network access. Do I these URLs need to be accessible on all Exchange Servers or just Hybrid Server is enough ?
The other thing you advised is that if I disable On Premise IOC and populate OrganizationRelationship with https://outlook.office365.com/ews/exchange.asmx Free / Busy look up will not use Autodiscover but it will use EWS and that may resolve my issue ?
Also I will have my network team allow outbound connections to anywhere on port 80, 443 for a small duration to test and let you know if that worked.