Subscription to the ML limited

Hi,
  since a couple of months the ML is receiving some SPAM attacks.
Subscribed users are not affected however some external scripts try to
subscribe new users possibly posting new requests to the web (I suppose).
I tried to contact the server administrator but after 3 mails and a months or
so I didn't get any feedback.
I was quite bored having to disable manually lot of users so yesterday I
decided to disable the subscription using either e-mail and web and I
put some notes on the information page asking to open issues in GitHub.
Does somebody knows how to contact the server administrator?
Can somebody suggest some Mailman configurations I can make to
avoid such attempts?

Regards,
   Frediano