Outlook prompting for credentials

Client has Exchange 2013 STD running on a hyper V instance.  They have been running  fine until this morning, the all users are getting prompted for username/password when the open Outlook.  When they enter the information, the credential box just keeps refreshing as if nothing or the wrong information was entered.  If they use OWA they can login and read email fine.  I am not seeing any obvious events in the logs, and all services are started and running.  I rebooted the Exchange server, host and domain controller, nothing helps
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Berkson WeinTech FreelancerCommented:
Are the users connected via the LAN or remotely?
Nick RhodeIT DirectorCommented:
Using basic or NTLM authentication for exchange?  Also is there a proxy in place by chance that needs to be tweaked?  Another thing you can try is to check DNS to make sure they are pointed correctly.

Another option is to open outlook and in the system tray do a ctrl + right-click and try a Test Email Auto-Configuration

Uncheck everything except Use Autodiscover
Brent ArnoldTechnicianCommented:
I would make sure that you don't have any old/new entries in your DNS forward zones pointing to old email servers.
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Will SzymkowskiSenior Solution ArchitectCommented:
Issues like this usually relate to Autodiscover issues and also the type of authentication you are using. In the outlook client under the Security are you using Negotiate Authentication? Also can you hold ctrl+right click the outlook icon in the system tray and select "Test E-mail auto configuration" perform the Autodiscover test. Also using the same method, hold ctrl+right click and select Connection Status. Check to see what servers your client is trying to authenticate to.

This could also be misconfigured Authentication settings on the virtual directories as well.

Berkson WeinTech FreelancerCommented:
Running these powershell commands will get you some info (lots):

Get-OutlookAnywhere | fl
Get-OabVirtualDirectory | fl
Get-WebServicesVirtualDirectory | fl
Get-ActiveSyncVirtualDirectory | fl
Get-ClientAccessServer | fl

I asked originally where the users are connecting from (and how) to see if it could be a a Basic vs NTLM authentication settings error.

When the users enter their credentials, does it work?
Outlook requesting for credentials could be cause for several reasons.

The most common seems to be a problem of credentials, not with exchange but with the DC.  If for some reason your server (exchange) is not in sync with your DC you will have problems.  So for this, you should make sure that time is the same in both servers, computer's time match server and that your domain controller was running when Exchange server rebooted (updates) cause some servers reboot faster than others depending on their roles. Ergo... wait for DC to be fully operational and then boot up your Exchange.

Always make sure user is entering "Domain\username" and password combination and select to remember this before they hit "Enter key".

The last one include to things that go together DNS and certificates.  These 2 should be correct in your case as they where working fine before.

Please check all these and let us know.
Simon Butler (Sembee)ConsultantCommented:
Do you have Windows 2003 domain controllers?
If so, then it is a suspect update. KB3002657. Remove it and reboot the DC and the problem goes away.


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rbarwigAuthor Commented:
Simon, et all;

Thank you for your responses.  Come to find out this all stemmed from the KB update number 3002657.  I was one of the first to report this to Microsoft and it was determined that the removal of the update AND a reboot of the Dcs at the client resolved this issue.
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