I use milter-null on all servers which works very well at rejecting bounces for mail I didn't send. I've also been testing milter-ahead which is going to be used on all of my relay boxes shortly to limit the amount of backscatter sent.
I would be a bit worried at just blocking/filtering just based on subject/sender/etc as per the last link as I do like to see issues with mail I did send
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ChrisB.