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, a

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.