idea: thread-scoring routine

I have this idea, maybe someone has already implemented it.

I setup a database of email addresses with a score based on my experience of the value of the content of their emails. Not a spam score, a content score. So I can say that randomuser21@hotmail.com typically posts worthless crap. Then I score them negatively in my db/table of users. Then something reads in my mailbox and adds a score to the subject line of threads based on the scores assigned to the users involved.

Then I can see if a thread goes up or down content-wise based on who posts to it.

I’m pretty sure I can do this with procmail but I’m curious if it has already been done.