Richard Rosner writes:
And yes, while there may be edge cases where these bad practices
If you're willing to impose that judgment on your posters, just announce that you're going to start discarding posts that don't satisfy From alignment, give it a week, and start doing it. That will ensure that the Sender is always in the From field. No more, and no less. I wouldn't do it, but it's a perfectly effective way to achieve what you seem to believe is ideal.
And until someone can create an ML model that's not gobbling up resources for training and that doesn't need thousands of emails to train with, there's only so much you can do.
SpamBayes has been around for decades.[1] It's not ChatGPT-level, but it also doesn't take "significant resources" or thousands of emails for training (your current spambucket and INBOX will be a decent start) and you can train it on the fly as mail comes in. The only resources required are a couple of hours to install it and learn how to feed ham and spam corpuses into it, and a few minutes every so often to feed increments of ham and spam to it. You can even avoid that amount of effort by feeding the spam and ham it outputs back into it.[2] Almost certainly you can plug it into rspamd.
While DKIM and DMARC are great, they are useless when the vast majority of senders don't have any DKIM signatures. For ARC it's not as uncommon to be present, but the situation isn't that much better.
Please stop. These claims are not going to pass on this list. We know better.[3] If you are in a special situation where they bear some resemblance to the truth, please explain. Maybe we can come up with a solution for that situation together. But they are wildly wrong in the context of Internet email in general.
Look, Richard, spam is extremely frustrating to all of us. There's a lot of effort and talent that has gone into combatting spam, and a fair amount of knowledge about it has accumulated in the people who participate in Mailman lists. If you want help with the particular spam that's getting into your lists, we'll be happy to help (although help channels for your preferred filtering software might be more productive). But the way to get help is to explain what your problem is, and what you've done that isn't working, in some detail.
You telling us how we can fix it in Mailman is almost always a non- starter. Either it's going to screw up the mail system with little anti-spam effect, or it's been tried and shown to be ineffective. It's certainly not persuasive if you haven't shown us what the problem is at a more granular level than "we all hate spam!" It's possible that we'll come back to your suggestion sooner or later. Sometimes there's no other way that's better. But that's quite rare. ;-)
Footnotes: [1] In fact, I've recently seen the (otherwise unsupported ;-) claim that spam-filtering was the original motivation for ML research. :-)
[2] This leads to overfitting and increased error rates after a while. YMMV.
[3] For example, in my current spam-bucket, all of which I've eyeballed, there are 7519 Message-IDs and 9521 DKIM-Signatures. Of 206 messages from external sites in my now spam-free INBOX, there are 336 DKIM-Signatures. Since it's common to have more than one DKIM-Signature per message, that doesn't prove that essentially all of those messages are signed. But it sure seems likely! And ARC is much less common: 4903 ARC-Seals in spam, and 155 in INBOX.