Recently, I had started migration of mailboxes to Microsoft Exchange 2013 CU1. As I started to move accounts over employees begun receiving prompts to enter their credentials for Outlook 2010/2013 and sometimes Lync 2013. These prompts had appeared during the opening of Outlook, Lync and intermittently thereafter. Reading two different articles one from TechNet: After Migration to Exchange 2013 – Credential user keep prompting on Outlook 2010 SP1 and Microsoft KB Article: Users of Exchange Server 2013 or Exchange Online can’t open public folders or shared mailboxes on an Exchange 2010 or Exchange 2007 server, I had tried different solutions ranging from changing authentication protocol to NTLM to Kernel-Mode Authentication for RPC and other virtual directories. The irony in all this, I had run into a similar issue with Exchange 2007 several years earlier.
Here are the steps I had to perform to fix this issue.
1. Logon to Exchange 2013 CAS Server.
2. Open IIS 7.0.
3. Locate virtual directories for Autodiscover and EWS (Exchange Web Services) under default website.
4. Select EWS.
5. Select authentication.
6. Set status DISABLED for Anonymous authentication.
7. Select Windows authentication, click ADVANCED SETTINGS, select ENABLE KERNEL-MODE AUTHENTICATION. Click OK.
8. Repeat Steps 5-7 for Autodiscover.
9. Go to command prompt, run IISRESET.
10. Close and re-open Outlook client.