SECURITY
User Web browsers must have cookies enabled since the authentication token that is generated by the server is sent to the browser in a cookie.
You set this up by doing the following:
Checklist for enabling single sign-on
The SSO feature makes logging in and using multiple servers in a mixed environment easier for users. Use the following list to configure your Domino environment to ensure that your SSO configuration is successful.
General issues
See the multi-identity section (probably this would be the topic on configuring LTPA user names, as well as the topic that covers the DA feature "Attribute to be used as Notes distinguished name" ).