After the upgrade to CU3 on all my Exchange Servers, some of the end users started complaining about username and password popups. Password was entered but the box kept on appearing.
Check credential manager and all seemed fine. I then went and had a look at my Exchange Server. After running the command: Get-OutlookAnywhere I noticed my main server had the correct settings but the rest were mixed with Basic, Negotiate and NTLM.
I removed Negotiate and set them all to Basic,NTLM and ran an IISReset on each server. After this all outlook clients connected fine. Here is the command:
- Set-OutlookAnywhere -Identity ‘<ServerName>\rpc (Default Web Site)’ -IISAuthenticationMethods Basic,NTLM
Hope it helps!