What is One-click unsubscribe?
One-click unsubscribe lets a recipient opt out from a button in their mail app, without visiting a page or confirming, using the List-Unsubscribe and List-Unsubscribe-Post headers.
Also called: List-Unsubscribe header.
Mail apps such as Gmail show an Unsubscribe link next to the sender's name when a message carries the List-Unsubscribe header. With the List-Unsubscribe-Post header as well, one click sends the opt-out to the sender's server directly. The recipient never leaves the inbox.
Google's sender guidelines require one-click unsubscribe on marketing messages from bulk senders to Gmail, those sending more than 5,000 messages a day, and Yahoo's rules mirror Google's. Separately, CAN-SPAM requires every commercial email to offer a working way to opt out, keep it working for 30 days after sending, and honour requests within 10 business days.
For cold email, an easy opt-out is also self-interest. A recipient who cannot find one clicks Report spam instead, and that raises your spam complaint rate.
Every opt-out belongs on a suppression list shared across all your tools. The CAN-SPAM checker checks an email draft for an opt-out and the other required elements.