Failure: repeated attempts to unsubscibe

Hi all, I've attempted to unsubscribe my father repeatedly, following the
instructions at the bottom of each email -to no avail. Message says there
is no user called "unsubscribe@global.libreoffice.org".

My father has died. I'd appreciate assistance with his removal from this
list. Thanks!

Kathleen, Bill's daughter.

​Hi,

You have to send an email to the following address:
users+unsubscribe@global.libreoffice.org

You need the whole users+unsubscribe. Pay extra attention to the plus sign,
and make sure your email client isn't interpreting it as something else,
but really send the email to that exact address.​

Might the problem be the OP can't send the user+unsubscribe from subscribed email address?