Hi,
I noticed that AutoDiscover have passed the test through remote connectivity analyse.
Please confirm whether the issue happens to all users or specific users to narrow the issue to client side or server side.
If the issue occurs on all users, we could run the following command to check the autodiscover service.
Get-ClientAccessServer | FL Identity,AutodiscoverServiceInternalUri
We could check the autodiscover service with the AutodiscoverServiceInternalUri value to get the returned error code in IE. Also check the browsing following similar URL in your browser:
https://autodiscover.mydomain.com/autodiscover/autodiscover.xml
if the error code is not 600,please run the below command:
Set-ClientAccessServer -Identity servername AutoDiscoverServiceInternalUri
https://mail.mydomain.com/Autodiscover/Autodiscover.xml
Then restart IIS service by running IISReset from a Command Prompt window to have a try.
regards,
David