Hi,

I administrate two small, public Mailman servers.

On one of them [1], I see a lot of unsolicited subscription requests.
For example, win**********ad@gmail.com was subscribed 41 times last week, from 13 different IP addresses. A whois search on these IP addresses suggests they're from anonymization services or spam-friendly hosting companies.

In total, there were 234 requests last week, the vast majority were unwanted.

Does anyone have any advice on preventing this abuse? Subscriptions require confirmation from the user, so manual approval won't help -- there's still a notification that the request awaits manual approval.
Preventing sign-up from a dodgy IP is one option, perhaps directing users to email the list owner if they have been caught incorrectly -- has anyone set up anything like this?

Thanks,

Matt Blissett

[1] lists.tdwg.org