Hi I'm having a strange issue where some users are saying their Outlook is prompting them for credentials when they open it / re-open it etc. I've tied it down to one city where there is one mailbox Exchange 2007 mailbox cluster, one CAS, one HT, and two DC's (one of which is a GC). Does anyone know what would be causing this? I can't see anything in the Exchange event log to say there's an issue with connecting to AD.

Did you check autodiscover connection from outlook client and see any alerts. Go into outlook tray in task bar , Ctl+Shift+mouse pointer to outllok icon and select Test outlook connection. Here select "autodiscover" and put credential. Also check where you see any problem of kerberose authentication in DC's Anil

Hi Redman, Any update for your issue? I want to verify some information from you: 1. which version of exchange and outlook do you use? 2. How many users have the issue? 3. Are the issue users in the internal domain network and using mapi, or are from the external domain with using outlookanywhere? 4. Did you check the issue mailbox in person to cnfirm it on other box? And then we could narrow down the issue, I would do some troubleshooting as below: 1. update all the exchagne 2007 server for the latest version 2. use test-outlookwebservices to confirm some information 3. follow Anil's suggestion 4. confirm the authenaction method on the VDs of the CAS server are configured properly. Regards! GavinPlease remember to click Mark as Answer on the post that helps you, and to click Unmark as Answer if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.