Two mechanisms, one older and one required
RFC 2369 defined the original `List-Unsubscribe` header, carrying a `mailto:` address, an `https:` URL, or both. RFC 8058 added `List-Unsubscribe-Post`, which turns the header into a genuine one-click action: the mail client sends a POST request on the recipient's behalf with no page load and no confirmation click required, rather than opening a browser tab to a page the recipient still has to interact with.
Gmail and Yahoo made this non-optional
Starting February 2024, both Gmail and Yahoo require bulk senders — roughly defined as anyone sending more than about 5,000 messages a day to their users — to include a working one-click List-Unsubscribe header, alongside a complaint rate that stays under roughly 0.3% as measured in Google Postmaster Tools. Missing the header on qualifying bulk mail risks outright rejection or heavy throttling, not just a lower engagement number.
It has to actually work, not just be present
A header pointing at a broken link, a page that requires login before showing an unsubscribe option, or a POST endpoint that doesn't actually process the request satisfies the letter of having the header while failing the requirement it exists to meet. Providers increasingly verify that the mechanism functions, not merely that the header is syntactically present.
This is a separate signal from account-level suppression
List-Unsubscribe is a per-message, recipient-initiated opt-out mechanism a sender has to build and honor — distinct from SES's account-level suppression list, which is populated automatically from bounces and complaints. A recipient who unsubscribes via this header should be removed from future sends by the sender's own list-management logic; SES's suppression list has no visibility into that action at all.
Why it matters
A working one-click unsubscribe is now a deliverability requirement, not a courtesy — for bulk senders on the two largest mailbox providers, its absence is treated the same as a policy violation, and it's also the mechanism that gives a frustrated recipient somewhere to go other than the report-spam button, which directly protects complaint rate.
Common questions
Is List-Unsubscribe required, or just good practice?
For bulk senders — roughly 5,000+ messages a day to Gmail or Yahoo users — it's required as of February 2024, alongside a complaint rate under about 0.3%. Below that volume it's not mandated by either provider, but it's still good practice everywhere.
What's the difference between List-Unsubscribe and List-Unsubscribe-Post?
List-Unsubscribe (RFC 2369) names a mailto: or https: destination. List-Unsubscribe-Post (RFC 8058) is what makes it one-click: the mail client POSTs the unsubscribe request automatically, with no page load or confirmation click needed from the recipient.
Does List-Unsubscribe feed into SES's suppression list?
No. It's a separate, sender-managed opt-out mechanism. SES's account-level suppression list only reflects bounces and complaints — a recipient who unsubscribes via this header has to be removed from future sends by the sender's own list-management system.