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I did this with procmail 20 years ago: http://angel.net/~nic/spam-x/procmailrc.txt http://angel.net/~nic/spam-x/procmailrc.txt – and then stopped because lots o
by nicwolff 8y ago
I did this with procmail 20 years ago: http://angel.net/~nic/spam-x/procmailrc.txt http://angel.net/~nic/spam-x/procmailrc.txt – and then stopped because lots of spam comes with random people's real e-mail addresses as the From, and my challenge autoreplies were quite rightly being reported as spam by their innocent recipients. Now I just use FastMail and let their excellent Bayesian filtering do its job. (Oh, and I filter all mail with "unsubscribe" in the body into a "Bulk Mail" folder".)
- Operyl 8y agoMmm. I have transactional emails in my boxes that still have unsubscribe in the body.
- JimDabell 8y agoBetween then and now, that problem was solved – you send autoreplies to the Return-Path header, which is protected by SPF.
- dredmorbius 8y agoSMTP-time rejection, with a mechanism for specifying workaround ... doesn't exist, but if it did could address this failure mode of challenge-response.
- rakoo 8y agoIt kinda does, it's called greylisting and already works today: the recipient basically says "can't right now, please come back later". A spammer will not bother even reading this and will hit other targets. A proper smtp sender that dutifully respects the specs (the legit ones do) will try again up until a few days later, where the recipient can whitelist the sender. It's all automatic so it kind of doesn't solve OP's issue, but I feel like there should be a proper way to handle the challenge-response part.
- dredmorbius 8y agoGreylisting (e.g., greymilter) has long existed, but lacks a strong and reliable notification / remedy mechanism. It seems reasonably effective and non-noxious.