Looking at the header of your mail (`t' in gnus :), you'll see this line: List-Unsubscribe: <https://lists.gnu.org/mailman/options/emacs-orgmode>, <mailto:emacs-orgmode-requ...@gnu.org?subject=unsubscribe>
So, did you try to send an email to emacs-orgmode-requ...@gnu.org with the a subject "unsubscribe" ? hth Memnon
