Have you updated your email address to those old posts you have made to message boards? Is it possible that there are old messages you have sitting out there with your old email attached?
While you can't change the old posts, you can post new messages to the same board or list, restating your problem and including your new email. That way someone who finds the old post and your old email address can then search and find your new one.
I searched for one of my old email addresses and got over 1,000 hits. Some are for articles I wrote years ago, but a few probably are for posts to message boards on family members. Try searching for your old email address and see how many times it comes up. Have you posted updates to those boards?