[dpark]

Are you saying that email scanners were not only fetching the unsubscribe link but also submitting the “unsubscribe” button/form on the page?

I find this hard to believe since everyone else seems to manage this without a Captcha.

[yencabulator]

I does sound like they made a HTTP GET request have side effects.

[dpark]

I suspect that’s exactly what they did. And then they “solved” it with a Captcha. Conveniently I bet human unsubscribes also dropped when that was instituted.