I recommend you log into your web server’s admin and look for some mysql tool, like phpmyadmin.
From there you should be able to find the mailing list users table.
You can run a sql query something like this:
SELECT emailAddressColumnName FROM mailingListTableName;
That should output all of those for you.
From there, you might have an option to do a csv export.
If that doesn’t work, then perhaps you can hire someone from the concrete5.org jobs forum to write a simple export script. It shouldn’t be more than a couple of hours work for someone.