It should be under domain specific settings in the system admin login. So login under the system admin login, the first page you should see will have a list of the domains and different colored buttons at the top: spool, user activity, connects, ids blocks, server blacklist. Click on the name of the domain you want to change and you should then see a page with domain specific settings. The e-mail box is on the left, and 4 boxes down. In there is the settings for