I have to hold my hands up and say that I was not entirely happy with one of my answers from the Vancouver TechNet Winter Tour 2005 event Q&A session...
The question asked was 'how do you enable forms based authentication in ISA 2004 for Outlook Web Access Publishing'. The answer I gave was incorrect, so here goes:
Forms based authentication needs to be enabled on the web listener and is not part of the Mail Server Publishing Wizard. The procedure for enabling forms based authentication is:
In ISA Server Management, select the Firewall Policy node. In the task pane, select the Toolbox tab and the Network Objects header.
In the Network Objects header, expand Web Listeners. Double-click the Web listener you created for Outlook Web Access publishing to open its properties.
On the Preferences tab, under Configure allowed authentication methods, click Authentication.
In the list of authentication methods, clear any authentication method that is selected (the default is Integrated), and then select OWA Forms-Based. This establishes forms-based authentication for the Outlook Web Access Web listener, and for the mail server publishing rule that uses this listener. You use the steps that follow to configure idle session time-out and attachment control options.
Under Configure OWA forms-based authentication, click Configure to open the Outlook Web Access Forms-Based Authentication dialog box.
There is a full description of the procedure for securely publishing Outlook Web Access in the document: http://www.microsoft.com/technet/prodtechnol/isa/2004/plan/owapublishing.mspx
I have there