..."@sendemhere.com" in your submissions? My directory gets a couple of these on a daily basis where the email extension they submit is @sendemhere. It's always a Real Estate company and the email address always bounces. Now, I find the right email address of the Real Estate company and ask them why they are using a bogus email address to get a free link. The responses are great... they all get angry at either me or the service they atre using for SEO... I'm hoping that the joker that continues to use that as a return email address gets the point and stops submitting fraudulant email addresses or loses business because of it.
If you only want genuine email addresses, why don't you put a email confirmation mod in your directory? It's becoming very popular with directories anyway.