I've finished setting up Exchange 2007 and everthing works great with one exception. I'm having a problem with Outlook 2007 clients specifically on computers that are not members of the domain. It conistently prompts to enter the password everytime Outlook is opened. I have Outlook 2003 clients that this is not a problem with once I do the registry hack to change "Incompatibilitylevel" to 3. However, this doesn't help with Outlook '07. I've tried every combination of security settings between Outlook and IIS and Exchange Management Console to no avail for both NTLM and Basic. I've confirmed that settings were consistent across all applications but I can't shake this. I do not have an ISA server and it isn't a firewall problem because my Outlook '03 clients work fine.