Poco Filter FAQ - Filtering by known or unknown email addresses (Whitelisting)

Q:Is it possible to set up a filter that will select only messages from either known or unknown recipients? By "known" I mean only those people who are in one of my address books.
Yes, select "Known Senders" from the drop down list in the filter's "search for" box :

There are other documents in the FAQ that explain the other choices show above as well as a list of undocumented options.

To look for the opposite of any of these groups (for example, to look for unknown senders), check the "Match only if not found" box at the left of the filter box.

Yes, using the undocumented %addressbooks% filter search argument you can achieve this. eg:

Conversely to filter for unknown recipients use: