The best scenario is be able to classify the type of bounce: soft, hard…
what we use is BounceStudio. You need to compile it and add the php libraries… not hard at all. You have the free and paid version of that product
once we detect the kind of bounce we use PEAR::MAIL::MIME to search for custom headers that we added previously to the email, lets say:
X-user-id: XXXXX
X-campaign-id: YYYYYY
X-recipient-id: SSSSSSSSS
in this way we can know the real recipient that we sent the email to.
hope this help you! so you can help me to get to the 500 points 😛