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We have an Exchange Environment with 2 X Exchange 2016 servers and 1 X Exchange 2019. EX2016 is running on Server 2016 and EX2019 on server 2019. One issue we are experiencing is when Outlook clients connect via the EX2019 server and their mailbox resides on the EX2019 server, the mailbox opens fine. If they are then opening shared mailboxes or mailboxes with delegated access which reside on either of the Exchange 2016 servers, they are not able to view the mailboxes. The Outlook connection status just shows as 'Connecting' and an 'Error' status under Authn.
If they connect via either of the Exchange 2016 servers, all works completely fine!
As testing on this, I am simply connecting from a remote PC running Outlook 365 and changing the NAT rule to point to either the EX2019 server (which doesn't work) or the EX2016 server (which does work).
As far as I can see all settings on virtual DIRs are identical.
ExcludeExplicitO365Endpoint added to reg
Has anyone experienced this issue or got any suggestions, please?
Thank you in advance.
Morning Jayce, unfortunately this doesn't appears to be a Cypher issue. I currently have a support request open with Microsoft who haven't been able to resolve the issue so far. I will provide a further update once Microsoft has found the cause, so that this can be shared with the community.
Kind regards - Paul
Thank you for sharing the information with us. We appreciate your efforts and are eagerly waiting for your update on the issue. We hope that the issue can be resolved soon.
Could be a TLS issue. Ensure they are set to TLS 1.2
Any reason you are not running all 2019?
Thanks Andy. I will go through your article to check the points mentioned. We will be moving the customer to EXO later this year, with a Hybrid setup with the EX2019 server remaining on premise. I will provide you with a further update once I have gone through the article provided.
Thank you again for your kind assistance.
Just circling back to check to see how things are going on with this thread. Should you need more help on this, you can feel free to post back.
If Andy's answer is helpful please click on ACCEPT ANSWER as it could help other members of the Microsoft Q&A community who have similar questions and are looking for solutions.