Outlook prompting for password for SOME users since migration from Exchange 2003

I've had various "issues" along my migration path, and thanks to EE, these have all been sorted.

The scenario:-
Customer has recently been migrated from Exchange 2003 as part of SBS 2003 to Exchange 2010. All mailboxes, public folders etc have been migrated. Routing group connectors etc have been removed, and Exchange 2003 has now been uninstalled from SBS 2003.

All users are on Outlook 2010 (32-BIT) and SOME internal users are being prompted for credentials. Upon inspection, it would appear that RPC over HTTP has been enabled for all users. If I turn off this option within Outlook, then those people who WERE being prompted for credentials then work OK.  One user claimed that if she simply cancelled the prompt that she was still able to send and receive emails OK, whereas another user claims that he cannot.

Both the InternalURL and ExternalURL are set as https://exchange.mydomain.net/ews/exchange.asmx

The internal DNS correctly resolves to the internal URL for exchange.mydomain.net

AutoDiscoverServiceURI is set as https://exchange.mydomain.net/autodiscover/autodiscover.xml

What else could be the problem?
LVL 17
Chris MillardAsked:
Who is Participating?

[Product update] Infrastructure Analysis Tool is now available with Business Accounts.Learn More

I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

Will SzymkowskiSenior Solution ArchitectCommented:
I would be checking the Authentication you are using on your virtual directories. Also what authentication is configured within the Outlook client? I would set it to Negotiate if not already. Also, on an affected user do the following...
- open outlook
- hold ctrl+right click the Outlook icon in the system tray
- check the connection settings (to see what servers their Outlook is trying to connect to)
- also run the Test Email Auto Configuration (running the Autodiscover test, make sure that all of the virtual directories the client is using are correct).

Also check the applicaiton log on the Clients machine as well.


Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
Chris MillardAuthor Commented:
I've not been in a position to check the above yet, but I contacted the customer for an update and have been informed that no one has (so far) reported this problem since the beginning of last week.
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today

From novice to tech pro — start learning today.