Need help to get unsubscribed

Hello,
please could someone help to unsubscribe me from schema.org mailing list.
I tried to do it myself by sending a mail to public-schemorg-request@w3.org
with subject unsubscribe and I get the response by email, that it was
unsuccessful because my address archinf@archinform.de ist not registered in
the list ???
What should I do?

Sincerely, Sascha