Deliverability
List-Unsubscribe header generator
Build the List-Unsubscribe and List-Unsubscribe-Post headers RFC 8058 one-click unsubscribe needs from your link, or nothing at all when the link cannot carry a POST.
Free, no accountIn your browser
An https:// link that acts immediately on a one-click request. A mailto: address on its own cannot support one-click and is rejected.
Added alongside the https:// link above, never instead of it - RFC 8058 allows an extra, non-HTTPS URI in the same header.
Result
Nothing to build yet
Paste the https:// link your unsubscribe page uses.
What this is
This list-unsubscribe header generator writes the List-Unsubscribe and List-Unsubscribe-Post headers a new outgoing message needs, from the https:// link your own unsubscribe page serves, rejecting anything that cannot carry a real one-click POST.
One-click unsubscribe works because a mail receiver does an HTTPS POST straight to the URI in List-Unsubscribe, with the fixed body in List-Unsubscribe-Post as the request (RFC 8058 §3.2). That only works when the URI is https:// - an http:// link or a mailto: address on its own gives the receiver nowhere to POST, so Gmail and Yahoo skip the button entirely and fall back to the slower flow instead.
How to read the result
Type the https:// link your own unsubscribe endpoint serves and both headers appear below, already in the two-line form RFC 8058 §8.1 shows: List-Unsubscribe with the link in angle brackets, then List-Unsubscribe-Post with the fixed body - one copy press takes both. An optional mailto: address is added alongside the https:// link, never instead of it, exactly as RFC 8058 §3.1 permits. A link this tool cannot build a one-click header from - http://, a bare mailto:, or anything that is not a URL - produces a finding naming exactly why, and no header to copy at all.
Our guide "What Google and Yahoo require from bulk senders, and how to prove you meet it" has the exact RFC 8058 wording both companies check for, and the other rules a sender passing this check still has to meet.
Common mistakes
What goes wrong most often, and how to tell.
- Publishing an http:// unsubscribe linkRFC 8058 §3.1 requires the URI in List-Unsubscribe to be https:// specifically, because the receiver POSTs to it directly (§3.2) - an http:// link is silently treated as unusable for one-click rather than merely insecure.
- Assembling the List-Unsubscribe-Post body by hand from piecesThe body has to be the single, exact string "List-Unsubscribe=One-Click" - building it from a template or concatenating strings at send time risks an extra space, a trailing character, or the wrong case slipping in, any of which a receiver treats as a different string entirely.
Questions
What people ask about this tool.
- RFC 8058 §3.1 requires the List-Unsubscribe URI to be https:// because a receiver does an HTTPS POST straight to it; an http:// link gives it nothing secure to POST to, so publishing the header anyway would ship a broken one-click button rather than a working one.
- RFC 8058 §3.1 allows a non-HTTP/S URI such as mailto: to sit alongside the required https:// one in the same header - it is useful as a fallback for an old client that does not support one-click, but it can never replace the https:// URI the POST actually targets.
- This tool names exactly why it was rejected and produces no header at all - an invalid target is never allowed to produce a copyable header that looks correct but is actually broken, the same restraint the DMARC record generator shows when an address fails its own check.
- No - it only builds the header from the link you give it. Confirming the link is reachable and already honours a one-click POST on the other end needs a real request, which the list-unsubscribe header checker next door reads a pasted header against this same syntax for, without ever sending one either.
Sources
Every fixed value here comes from the provider’s own documentation. These pages change, so each says the day it was last read.
- IETF, “RFC 8058 - Signaling One-Click Functionality for List Email Headers” read 13 October 2026
- IETF, “RFC 2369 - The Use of URLs as Meta-Syntax for Core Mail List Commands” read 13 October 2026
- Google, “Email sender guidelines - one-click unsubscribe” read 13 October 2026
Use it from the API
The same check, as one request.