After digging some more into the Osx Mail file structure I managed to get the desired folder and extracted it. Great Saved me a lot of work. Now I can delete all the bounced mail from our newsletter in one go!

@sweetp Hi I followed your sample. Thanks.
But it just gave me a massive import of all the 40000 e-mails. And than asked for the place to store the extract. Now that works but I need the mails (addresses) from on specific postbox only. Now I have all in one file messed up so no chance to select.
So, I was expecting an option for selecting only the e-mail folders I need. But did not get that. How to make sure it only take an certain folder and not the whole bunch? Thanks.

Just bought the Mac eMail Address Extractor. Now I am a bit lost. I want only to extract a specific mail-folder (postbox) holding bounced mails. How to extract that selected Osx Mail folder? Seems not just dragging it into the program window. Where to select the needed files? Any help appreciated.