Misconfigured virtual directory URLs and certificates can cause problems with Outlook. Common issues include password prompts and certificate warnings.
Outlook uses autodiscover to configure itself with the correct hostname for Outlook Anywhere, the correct URL for web services to set Out of Office and the correct URL for the Offline Address Book download for example.
These URLs and hostnames are set on the Exchange server using cmdlets like Set-OutlookAnywhere and Set-OABVirtualDirectory but these will be covered in a separate post.
To confirm that Outlook is using the correct URLs, use the Test E-mail AutoConfiguration utility which is built into Outlook.
1) Hold down CTRL and right click on the Outlook icon on the system tray (bottom right of the screen)
2) Tick Test E-mail AutoConfiguration and untick Use Guessmart and Secure Guessmart Authentication
3) Click on Test
You can now see the Exchange URLs that Outlook is configured to use. If you find that URLs are incorrect then these need correcting.
If you find that the virtual directories on Exchange are configured to use a different URL than what Outlook has reported, you can wait for Outlook to re-check its settings or you can repair your Outlook profile. If this still shows that Outlook is not using the correct URLs then it's likely that the settings were changed on Exchange quite recently and to make them take effect you need to restart the MSExchangeAutodiscoverAppPool on the CAS servers.