http://lmgtfy.com/?q=Extract+all+email+addresses+from+a+Gmail+accountAlternatively just google the topic subject and hit "I'm Feeling lucky"
Did that already. Didn't come up with anything useful just like your reply.
The labnol one sounds right?
Had the same question last week. I used the instructions in the bottom of this post and it worked for me. http://webapps.stackexchange.com/questions/48453/how-to-export-a-list-of-all-emails-addresses-that-i-have-sent-mail-to-in-gmail
Ask the Prince from Nigeria. He does it all the time.