Help: spammers flooding my autoresponder

Hello There,

I’ve come here looking for a bit of help or advice regarding a dilemma that I am currently having for my website.

I host an auto-responder that doesn’t require a double opt-in. Anybody can come and create an account and they will start receiving our series of emails.

The problem is that I am being attacked by a persistent group of hackers/spammers that are installing bogus accounts and using proxies to do their work.

Although I’ve filtered all their IP addresses and eliminated the bogus email accounts, they still come at me every day! I’ve thought about using a CAPTCHA, but that will only slow them down, it won’t stop them, so my question is;

Is there some way that I can stop this attack, other than using a double opt-in???

I thank you for your help and look forward to your input.

This question interests me too as one of the sites which I run with my partner has also been spammed in a similar way as the Topic Starter has described.

I think there are some ways to block ips by country, you could try cutting off anyone from India, China, Singapore and other places which are likely to produce spammers.