It's the same for _all_ mailman mailing lists, let alone that nearly
all MUAs provide mailing list features, so you even don't need to take
a look at mailing list mail's headers.
The address to unsubscribe is _not_
jack-devel at lists.jackaudio.org
it is
jack-devel-request at lists.jackaudio.org
^^^^^^^^
^^^^^^^^
Hth,
Ralf