What is Postini
Postini is a third party application that some email users choose to run their email through. Although rarely used, we wanted to make this information available to help any that may have this problem.
Users cannot authenticate into their Postini account
When a mail server requires the username to be the full email address to authenticate, in Postini you must edit the 'Authentication Data' field (found in General Settings on the main screen) to include ,@USERDOMAIN on the end of your POP mail server name.
If you just have 'mail.domain.com' or an IP in there, and your server requires a full email address as the username, it will not work. This is because by default Postini uses the username portion only to authenticate to the POP server.
Change the "Authentication Data" field to "mail.your_domain.com,@USERDOMAIN" and the users will be able to properly authenticate into their Postini Message Center.