>Whenever gmail, thunderbird or office365 outlook notices a working unsubscribe link in a message, it puts its own unsubscribe link at the top of the message, r

>Whenever gmail, thunderbird or office365 outlook notices a working unsubscribe link in a message, it puts its own unsubscribe link at the top of the message, right next to the address of the sender's email. I've never seen such a thing. I just checked Thunderbird, on an email that has an unsubscribe link. There was no such button.