Question about scoring with sanesecurity signatures

[francis picabia]

Many of the signatures available with sanesecurity are rated to produce
false positives at a "medium" rate.  Their page:

http://sanesecurity.co.uk/databases.htm

suggests to score the detections rather than block.

How can I prevent amavis from blocking (flagging as INFECTED)
for specific clamav databases?

For example, I'd like to treat scamnailer.ndb as a DB I would
not block based on its match.