[Copied directly to George since he may only see this on the list digest]
George,
Sadly, this won't do it. You (and anybody else in this position) need
to follow the procedure described at the foot of each message.
You need to send a mail to debian-user-digest-***@lists.debian.org
with a subject of Unsubscribe and something in the message body.
That will generate an automatic response sent to you, asking you to confirm
the unsubscription request.
A reply to *that* message will act as your unsubscription.
Hope this helps, as ever,
Andy
(***@debian.org)