Unusual Exchange server troubleshooting

  Issue: Changes in Outlook shared calendar appointments are not accepted, just the window close with no error but the changes are not set, also can't delete, but can add a new appointment. The user is having full access to the shared calendar. The issue is only in Outlook, not OWA. Cause: It is one of the known issues with the new shared Calendar Improvements: Known issues with Outlook Desktop Shared Calendar Improvements - Microsoft Support Workaround: Creating new profile will make it work for a couple of weeks. What we did is to deactivate the shared Calendar Improvements option and reactivate it again. How to enable and disable the Outlook calendar sharing updates - Microsoft Support

  Issue: In an Exchange on prem environment Outlook prompts for O365 Password trying to connect to exchange online or Office365. and is not connecting after that. Cause: Moder authentication was enabled Solution: First, we thought of postponing the O365 request, by adding registry Dword (ExcludeExplicitO365Endpoint) this will tell Outlook to postpone the O365 Autodiscover request to the last. 1- Open Registry Editor 2- Navigate to: HKEY_CURRENT_USER\Software\Microsoft\Office\<x.0>\Outlook\AutoDiscover 3- 3- 3- Create new Dword : ExcludeExplicitO365Endpoint  value 1  but this didn't solve the issue  so we decided to disable Modern authentication 1- Open Registry Editor 2- Navigate to: HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\<x.0>\Common\Identity   3- Create Dword: EnableADAL value 0 DisableAADWAM  value 1 DisableADALatopWAMOverride  value 1 then the Prompt stopped and outlook connected to On-prem Autodiscover 

  Issue: Can't find msexchHideFromAddressLists Attribute in ADSI edit or in AD users and computers to change it for the users. Cause: In the environment there is only Exchange online, no exchange on Prem and there never was, so the MSexch attributes are not there. Resolution: We downloaded the Exchange server prerequisites on another domain joined server as in here: Exchange Server prerequisites, Exchange 2019 system requirements, Exchange 2019 requirements | Microsoft Learn Downloaded Exchange server ISO from here: Exchange Server build numbers and release dates | Microsoft Learn Mount the ISO and then we run the command: <Virtual DVD drive letter>:\Setup.exe /IAcceptExchangeServerLicenseTerms_DiagnosticDataON /PrepareSchema and the Attribute appeared.

 Issue: Calendar sharing option is not available neither in OWA nor in Outlook, So can't share the calendar. Cause: After checking OWA we found that it looks different. Like in here:  Outlook Web App opens in the light version - Exchange | Microsoft Learn and as we checked this is the light version, but the customer didn't activate it and we can't undo the Light version option. it turns out to be the web browser version not compatible. Resolution: we tried to log in in a different computer with a higher windows version, OWA and Outlook worked fine. Other Information: If your Browser version is not the Problem, then you can revert to OWA normal version by: 1. In Outlook Web App, select  Options . 2. In the navigation pane on the left, select   Outlook Web App version , and then clear the   Use the Light Version of Outlook Web App   checkbox. 3. Select   Save   at the top of the page. 4.Sign out of Outlook Web App. The next time that the user signs in to Outlook Web App, the

 Issue: We Spotted that, exchange server is trying to connect to MS Teams IP addresses on UDP 137 the IPS are 52.123.134.179  -  52.123.135.179  Resolution :  first of All these IPS related to Microsoft Teams as per the link here Microsoft 365 URLs and IP address ranges - Microsoft 365 Enterprise | Microsoft Learn we can say that it is not a normal behavior from Microsoft, but at least the environment is not compromised.   and to stop the unwanted connection we deactivated NetBIOS.