The recipient obviously didn't think they wanted the email. For
mailing lists/broadcasters, this means it's an opt out request.
That would be fine, we could auto process them and remove those
addresses from any lists they've joined (might be a few false
unsubscribes but after they've resubscribed a few times they might
figure it's not a good idea to report it as spam) but firstname.lastname@example.org
isn't on any of our lists.
If this was to be more than a token system we'd be happy to support
a specific unsubscribe message for those than wished to leave our lists
and didn't mind supplying details. We'd also happily supply details
of our lists so their system would know there is no point treating it
as spam "you are reporting a mailing list you've subscribed to as spam,
do you want ot unsubscribe?" etc. I'm sure most on the list could cook
up a system to do this properly.