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