This tip was sent to me from a good friend and business associate, John Lockett.
This procedure gets rid of the security warning in Outlook 2007, in cases where you apply a standard SSL certificate to the default web site, and the FQDN is different from the AD FQDN of the exchange server. First run the following commands in the Exchange Management Shell on your Exchange 2007 CAS so that we would have a backup listing of the current settings:
Get-Clientaccessserver | fl > backupCAS.txt
Get-WebServicesVirtualDirectory | fl > backupWeb.txt
Now change the settings to remove the warning.
Set-Clientaccessserver -AutoDiscoverServiceInternalUri https://public FQDN, as appears in the certificate>/Autodiscover/Autodiscover.xml
set-WebServicesVirtualDirectory "\EWS (Default Web Site)" -InternalUrl https://public FQDN, as appears in the certificate>/EWS/Exchange.asmx
Wait a few minutes for implementation to complete.