SPF
QueuedEnvelope authorization
Email deliverability
Send one email. See exactly how it travelled.
We check authentication, ARC forwarding evidence, one-click unsubscribe, reputation and the TLS certificates visible along the delivery path.
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Preparing test
Expires in --:--Send your email to this address
Preparing a secure test address…Leave this page open. The report will appear automatically when the message arrives.
1
Address issuedReady to receive
2
Awaiting emailListening now
3
Build reportUsually a few seconds
Creating your test address…
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Provider delivery outlook
Calculating likely delivery
Chance of success—
Message received
Your report is ready
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Checks queued for this message
DKIM
QueuedSignature and key validation
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ARC chain
QueuedForwarding authentication continuity
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DMARC
QueuedAlignment and policy
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One-click unsubscribe
QueuedRFC 8058 HTTPS and DKIM evidence
Explore unsubscribe evidence
Published vs observed
QueuedConfiguration correlated with this message
Compare configuration and message evidence
Reputation & blocklists
Queued
IP, policy and sender-domain reputation
0providers checked
0clean results
0listings
0timeouts / unavailable
No providers match this filter.
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Route TLS
QueuedCertificates seen on the path
Explore route and certificates
PTR
QueuedReverse DNS and HELO
Explore PTR evidence
Standards guide
What “one-click unsubscribe” really means
RFC 8058 gives mailbox providers a safe, machine-readable way to unsubscribe someone from bulk or list email without making them find a link, sign in or complete another form.
The email advertises it
A hidden List-Unsubscribe header supplies a secure HTTPS endpoint.
DKIM protects it
A valid signature must cover both unsubscribe headers so they cannot be substituted in transit.
The mailbox sends one POST
The recipient’s mail app can submit the unsubscribe request immediately—no webpage or login required.
Required message evidenceThe two headers MailCheck reads
List-Unsubscribe: <https://example.com/unsubscribe/opaque-token>
List-Unsubscribe-Post: List-Unsubscribe=One-ClickClaiming “one click” is not enough
- HTTPS endpointList-Unsubscribe contains a structurally valid secure URL.
- Exact POST signalList-Unsubscribe-Post declares List-Unsubscribe=One-Click.
- DKIM coverageAt least one valid DKIM signature protects both headers.
PassManual onlyBroken claimOptional / absent
Standards lifecycle
RFCs are normally marked Updated by or Obsoleted by when their status changes. We monitor the official record so this explanation can be reviewed if RFC 8058 is replaced.