List-Unsubscribe
A header field carrying a command — preferably a mailto, and in modern practice also an HTTPS URL — that lets a mail client offer a direct unsubscribe control instead of requiring the reader to find a link in the body.
In plain terms
The header that puts an 'unsubscribe' button in the mail client itself.
Why it matters for deliverability
Giving people an easy exit is the cheapest protection against spam complaints there is. A reader who cannot find the unsubscribe link marks the message as spam instead, and that costs far more.
What to do about it
- Add the header to every marketing and subscription message.
- Include both mailto and HTTPS forms.
- Process unsubscribes immediately rather than in a nightly batch.
Source
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).”
Checked 2026-08-29
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