Open a web browser - e.g. Firefox and go to login.postini.com
Log in to Postini using your email address and password.
In the upper right corner locate and click "My Settings".
To approve an entire domain of users like Cesa12 then use the "Approved Domains" box. Just click to create a new line of text and enter just the domain such as cesa12.k12.wi.us. No slashes no www nothing but the domain.
To approve a mailing list such as email@example.com use the "Approved Mailing Lists" box.
Be sure to click the Update. . . button under the box where you have made changes.