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Glossary

List-Unsubscribe

List-Unsubscribe is an email header that carries an unsubscribe address, so a mail app can show its own Unsubscribe button without the recipient opening the message.

Updated · By Otman Ounana · How we research

Why it matters when you send from your own Gmail

The header is defined in RFC 2369, which describes it as the command, preferably by mail, to directly unsubscribe the user.[1] For cold email it is the polite exit. A recipient who cannot find your opt-out line will press the spam button instead, and spam reports are what hurt a sender most. Honest Intros puts the header on every email it sends, with both a web link and a mailto address.

Example

A message carries List-Unsubscribe: <https://example.com/u/abc>, <mailto:you@yourcompany.com?subject=unsubscribe>. Gmail shows an Unsubscribe link next to the sender's name.

What to do

Look at a test message's original headers and confirm the header is there and its link opens. Also keep a plain opt-out sentence in the text, because the header is the second route, not the only one.

Related terms

All terms are on the glossary.

Read next

  • RFC 8058 explainedWhat RFC 8058 one-click unsubscribe requires: the two headers, the HTTPS POST, DKIM, why it exists, and who now demands it (Gmail, Yahoo).
  • One-click under 5,000 a dayGoogle's one-click unsubscribe rule starts above 5,000 messages a day. What still applies below that, what the law asks for, and why a one-click link is worth adding anyway.
  • Bulk senderA bulk sender, in Google's definition, is any sender that sends close to 5,000 messages or more to personal Gmail accounts within a 24-hour period.
  • DKIMDKIM (DomainKeys Identified Mail) is a way for a sending server to sign each message with a private key, so the receiver can check the signature against a public key published in the sender's DNS.

Sources

  1. IETF, RFC 2369: The Use of URLs as Meta-Syntax for Core Mail List Commands. “The List-Unsubscribe field describes the command (preferably using mail) to directly unsubscribe the user (removing them from the list).” Read on 1 October 2026.