I am publishing an Exchange 2010 CAS behind ISA 2006 SP1. The same public UC certificate is on the CAS server and the ISA server with the subject name mail.domain.com and a SAN of autodiscover.domain.com.
Outlook Anywhere is using NTLM authentication.
External Outlook Clients connect almost immediately, (status bar says 'Connected'). A few seconds after connecting a credentials prompt pops up saying 'connecting to autodiscover.domain.com'. On entering credentials that is the end of it, all is fine.
I am trying to prevent that credentials pop up occuring, after all Outlook is already connected and new email appears. As far as I can see all the Exchange Virtual Directories have been set to use Basic and Windows Authentication.
Any clues about why the autodiscover url is prompting for credentials after Outlook is connected?
Should also mention that ISA is not authenticating the user but passing authentication straight throught to the CAS