In the Deliverability 101 session at the conference last week, Autumn or Kiersti said that there is a way to see which of your hard bouces were because of SPAM as opposed to an invalid email address. Anyone know how to do this?
Keep in mind that a lot of spam filters don't send an SMTP message back for a variety of reasons. You may have to look at the absence of a delivery confirmation or feedback from the intended recipient to know if your email was blocked.