After this latest round of Windows updates (on 1/11/11, in fact) my Exchange 2007 server of course rebooted. This may have had the side effect of making any changes I'd inadvertently made take effect.
Since then, the Autodiscover service in Exchange 2007 from Outlook 2007 seems to reply with the User Principal Name (
[email protected] instead of
[email protected]). I'm specifically seeing this from within the "Test Email AutoConfiguration" tool in Outlook (the UPN appears in the first text box labeled "E-mail") and when creating a new profile in Outlook. If I disregard the UPN and instead fill in my email address, Autodiscover works as expected and I can connect without issue.
I've confirmed using ADSI Edit that the SMTP email address is properly set for my users. I even went a bit crazy and set the UPN to the email address using ADSI Edit. I've re-installed the Client Access role on the server in question.
Exchange server is Server 2008, 64-bit of course. Clients are mostly XP 32-bit, though the issue happens from a Windows 7 machine as well.