Fix: When using Outlook 2007 you receive a prompt that is asking for a username and password.
Usually the prompt box text says autodiscover.domain.com
This issue is related to Exchange CAS server IIS SSL settings.
Note: This fix apply to Microsoft Exchange 2007 and 2010
To fix this problem we need to change the SSL settings to accept the user certificate.
To change the IIS SSL settings follow the steps below:
Open IIS Manager -> Sites -> Autodiscover virtual directory
In the right panel select SSL Settings
Change Client certificate from Ignore to Accept