Spammers have SPF and DKIM set up for their domains, too. Why does it seem so impossible to you that if mail hosters see "this IP block hosted a lot of domains that turned out be spammy" they react with "block it" or at least "block it if new sites pop up there"? (and as a private user, you're often enough "new" because you don't send all that much mail)

Yes, it'd be nice if they didn't do that, but small sites are and will be acceptable collateral damage to them.

SPF / DKIM let you know that who you think you're receiving mail from and who you're actually receiving mail from are the same person. How that that come into this at all? Spammers can say they're from onlinechemist@spam.com via SPF / DKIM and it's still going to come through.

I don't know who you're even trying to convince. You're talking in hypotheticals and being extremely idealistic. How the email ecosystem works and how it actually works are two very different things. You cannot say "the reason must be something else!" as if - just because you can't make sense of the situation - it is not so.

> What is the motivation for the "guilty by association"?

One that has been given in the past is "Stop paying money to companies that host spammer websites and spammer email servers, or we'll block your email too"

(I don't particularly agree with it, but it was common to see that argument on news.admin.net-abuse.email

Yeah, but they don’t identify themselves correctly. They lie.

Sometimes they claim to be real people with real e-mail addresses that they don’t actually own, and maybe that real person is you — in which case it is your reputation that gets permanently dinged.

Sometimes they claim to be fake people with fake e-mail addresses that don’t actually exist, in which case all you really know is the IP address they used to send the message. When they do this, they frequently arrange to get a large block of IP addresses they can use, and then cycle through them very quickly — maybe no more than five minutes per IP address. Anyone else who happens to be in that same range now gets their reputation dinged by association.

There’s a lot of tricks spammers use to try to hide their activity. And lots of ways to try to detect and reject that on the other end. It’s a never-ending arms race, and on the Internet it is easy to hide and hard to take out miscreants without causing excessive collateral damage.

And many big providers don’t care if they cause collateral damage.

Exactly. I also find this ridiculous.