You could create a segementation in your database for valid and invalid email addresses, and divide up the segments based on this criteria. It would allow you to have an idea of about how many people are unsubscribed vs. blacklisted vs. don't want operational emails. You could easily make a segment with a flow step like "if checks this box, then add to this segment" and then when you do the send, just avoid that segment. This would allow you to not 'taint' the number of blacklist vs actual unsubscribe.