fyi, this should also work as an alternative to using the web page to unsubscribe:
from mailman FAQ:
Open a mail program which sends mail from the address you want to unsubscribe. Send a mail to the list unsubscribe address, which will be of the form LISTNAME-leave@DOMAIN. The subject and body of this message will be ignored, so it doesn't matter what you put there.
so you may tell people they can just do this via a mail to glam-leave@lists.wikimedia.org
cheers,
the mailman server admin