White List Feature
As stated in the ACTIONS chapter, the White List button works a bit different:
If someone appears in your Unknown list and you want them added to your Known list but choose not to have them in your address book, simply highlight that message and immediately click the WL button.
Before you see the WL shown in the column above, you will first get this window showing the address has been added.
Click DONE and the next time you receive mail from this person, it will appear in your Known list.