A footer link is only part of the setup. Send us one campaign email and we'll check whether Gmail and Yahoo can show their own Unsubscribe button.
A footer link helps. Gmail and Yahoo also want one-click unsubscribe headers so they can show their own Unsubscribe button. We check both.
One-click unsubscribe is a pair of headers. List-Unsubscribe holds an HTTPS link. List-Unsubscribe-Post is set to List-Unsubscribe=One-Click. That lets Gmail and Yahoo unsubscribe a reader without opening a web page. RFC 8058 is the name of that rule.
We look for the word unsubscribe, or for any HTTPS link. An unrelated link can pass this row. It does not prove a visible unsubscribe link.
No. We read the message. We do not visit the link or send an unsubscribe request.