One-click unsubscribe header checker
Inspect unsubscribe URI syntax, POST marker and declared DKIM header coverage.
Your inputs
Your results
Ready when you areYour results will appear here.
How it works
Check the structure of one-click unsubscribe headers, an HTTPS URI, the exact POST marker and whether one declared DKIM h= list names both fields. Build a placeholder template without contacting the endpoint.
Read the source reference ↗A few things to know
A structural checklist, not RFC compliance certification or cryptographic DKIM validation. No endpoint testing, mail sending or unsubscription. Only common header unfolding and bracketed URI lists; ambiguous duplicate fields fail checks. Input capped at 100,000 characters.
When to use this tool
One-click unsubscribe depends on more than a visible link in a message. This checker inspects supplied header structure: a bracketed unsubscribe URI list, an HTTPS URI, the exact POST marker, and whether one declared DKIM header list names both required fields. It deliberately says declared coverage, because pasted headers cannot cryptographically validate a signature or demonstrate endpoint behavior. No unsubscribe URL is fetched or submitted. The downloaded template contains placeholders, so it cannot be mistaken for a provisioned working service. Keep real recipient tokens private when sharing a result.
- Review a sanitized message’s unsubscribe header structure.
- Find missing or duplicated one-click header fields.
- Prepare placeholder headers for a conversation with your sending provider.
How to use one-click unsubscribe header checker
Paste original headers
Include header names and folded continuation lines, not a full rendered message. Remove private recipient URLs before sharing output.
Read each structural observation
Check unique fields, bracketed list syntax, an HTTPS URI, the exact marker and one declared signature naming both fields.
Repair with your sending system
Use the placeholder template only after supplying a real HTTPS service. Validate signatures and endpoint processing in the actual sending system separately.
Five structural observations
Inputs
The example has an HTTPS unsubscribe URI, the exact List-Unsubscribe=One-Click marker and one DKIM h= list naming both headers.
Result
All five structural checks are satisfied. Declared coverage is shown for both fields in one signature.
What it means
The sample signature and endpoint are fictional. Passing these checks is not a validated DKIM signature or provider compliance certificate.
Common mistakes to avoid
Calling declared coverage signature validation
The tool does not have the original signed body or cryptographic verification.
Using a mailto-only list for this check
A mailto URI alone does not provide the HTTPS one-click endpoint examined here.
Testing a private unsubscribe URL by opening it
This tool never fetches URLs. Tokens can identify recipients; avoid disclosing them in reports.
Frequently asked questions
Definitions, edge cases, and practical next steps for this tool. Search all tool FAQs ↗
Does the tool send an unsubscribe request?
No. It parses supplied text locally, without fetching URIs or submitting POST requests.
What marker is checked?
A single List-Unsubscribe-Post field whose trimmed value is exactly List-Unsubscribe=One-Click. Missing, repeated or different values are flagged.
Can the URI list contain mailto too?
Yes, a bracketed list can include other URIs. The one-click observation still requires at least one supported HTTPS URI.
What does declared DKIM coverage mean?
One DKIM-Signature h= list names both list-unsubscribe and list-unsubscribe-post. This is a declaration, not proof that a signature validates.
Can two signatures each cover one header?
That does not satisfy this declared-coverage check. Both names must occur in the same signature’s h= list.
Why do duplicate fields need review?
Their meaning can be ambiguous and differ across parsers. The checker requires one unsubscribe field and one POST marker rather than selecting a convenient duplicate.
Will it prove Gmail compliance or show the mailbox button?
No. Sender scope, valid signatures, real endpoint behavior and provider policy must be checked separately. This is a bounded structural checklist.
What is in the template download?
Placeholder HTTPS domain/token fields and the one-click marker. Replace them through your sending system; the template does not create an endpoint or DKIM signature.
Sources and method
Use the references below to check definitions and platform guidance. The model’s scope and limits are explained above. Read our editorial standards.