Can I control the tooltips that are shown for each message classification in the dialog?

Yes.

In the janusSEAL for Outlook Lite Classification Dialog (popup), the end-user can obtain helpful descriptions of each message classification when they hover the mouse cursor over the classification. When they do so a tooltip is shown for a brief interval which can help the sender be sure they are using the correct message classification.

The text used for the tooltips is determined by the SenderDescription field that was assigned to the message classification when it was created on the Exchange 2007 Server in the Exchange Management Shell.

If you want to add or modify the SenderDescription field for a message classification then an Exchange Server administrator will have to use the Set-MessageClassification cmdlet in the Exchange Management Shell (see http://technet.microsoft.com/en-us/library/bb125250.aspx). Once the SenderDescription field(s) have been corrected then a new classifications XML file will have to be created and deployed to all end-user workstations.