How can I modify the scam filter?

I get a weekly email newsletter that is always identified as a scam. Each week I see a red bard identifying it as a scam, and I have to click it and say this message is not a scam. However, this does not update the scam filter. Shouldn't there be an option to add an email to a permanent 'not a scam' list? The junk filter gets updated as you say things aren't junk, the scam filter should work in the same way. Please consider this a feature request.