jens.guenther@posteo.de writes:
Same question here :-)
This is not a simple question. Mailman is built from the ground up on the assumption that users sign up. Making sign-up easy and powerful is the raison d'etre of Mailman.
One obvious approach is to add "^.$" to each list's ban list (eventually that should be configurable as a list style, so "easy" to make domainwide or sitewide), but that doesn't stop people from creating users via Postorius. One way to address that would be to clean out users with no subscriptions once a week or so.
I guess you could go into the templates and remove the accounts/signup/ links everywhere if "denial by obscurity" is enough, or into urls.py and send that URL to a "Get out of here you hacker!" view. Since these interventions are global, though, so the desideratum of "no site admin intervention" is right out. Users are site-global.