On Aug 22, 2016, at 01:03 PM, Franck Martin wrote:

While mailman does double opt-in, one can still fill a mailbox with account confirmations, what are the methods to stop a bot submitting email addresses for registration across several lists?

Mailman 3 will not pend a registration request more than once for an email/mailing list combination. It's possible to spam every list at least once though, and I'm not sure what you could do about that.

Cheers, -Barry