What is one-click unsubscribe?

A header is a line of hidden information attached to every email. Your sending system adds the two headers. The inbox provider reads them and can show its own unsubscribe control next to your message. The subscriber clicks once, and the inbox sends the request to your web address in the background. The standard forbids cookies or logins in that request and forbids redirecting it to another page¹.

There is a technical catch. RFC 8058 requires a valid DKIM signature (a cryptographic stamp showing the email really came from your domain) that covers both headers; without it, inbox providers should not offer the one-click option¹.

Your system then has to remove that address from marketing sends. That part is yours. The header only carries the request. Yahoo gives senders 2 days to honour an unsubscribe³.

No. The footer link is visible text inside the message body. One-click unsubscribe is built into the message headers, so the inbox can show it next to your message. Gmail asks senders of more than 5,000 messages a day for both: one-click unsubscribe and a clearly visible link in the message body².

The alternative to leaving politely is the spam button. When recipients cannot find the exit, some mark the message as spam instead. That hurts email deliverability, which is whether your email reaches the inbox at all. It also pushes up your spam complaint rate, the share of delivered messages that recipients mark as spam.

For the full list of what Gmail and Yahoo expect from senders, see Gmail Yahoo bulk sender requirements. For the money side of email, see customer retention strategy ecommerce.

For ZFD: We treat an unsubscribe as a cleaner list, and we judge email by margin, not by list size.