Establishing signal
LoadingEstablishing signal
LoadingGmail · Yahoo · Outlook sender requirements
One scan shows whether your sending domain meets the mailbox providers' technical requirements — SPF, DKIM, DMARC, alignment, one-click unsubscribe — with exact, copy-paste fixes.
Free, no signup. DNS lookups only — we never send mail from your domain.
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SPF · DKIM · DMARC · Alignment · RFC 8058 · MTA-STS · TLS-RPT · BIMI
01
Public DNS only
No credentials or DNS access.
02
Never sends mail
Your domain is read, not used.
03
Published rules
Provider requirements and RFCs.
04
Technical readiness
No inbox-placement promises.
Record present, single, syntactically sane, within the 10-lookup limit.
required
Selector keys published and strong — without false alarms when selectors are private.
required
Valid policy, reporting address, and verified report delivery — including external rua authorization.
required
From-domain alignment with SPF/DKIM, verified from a real message.
required
RFC 8058 List-Unsubscribe-Post — required by Gmail and Yahoo for bulk mail.
required for bulk
MTA-STS, TLS-RPT, and BIMI — the recommended tier, checked honestly (absence is a note, never a failure).
recommended
Already have a delivered test message? Paste its headers to verify DKIM, alignment, and unsubscribe compliance end-to-end.
01
Read the public records and a delivered message.
02
Use the exact record and plain-English next step.
03
Re-check daily and record what changed.
Agencies edit records, ESPs rotate keys, migrations drop a TXT record. Outlook has been hard-rejecting non-compliant bulk mail since May 2025 — most senders find out weeks later, from collapsed open rates.
Every daily scan diffs SPF, DMARC, MX, DKIM, and the hardening records against yesterday's. An include swapped or a selector rotated alerts you even when nothing 'breaks' — by email, Slack, or Discord.
Upload your aggregate reports and get an evidence-gated verdict on the none → quarantine → reject path: who is failing, when it's safe to tighten, and the exact next record to paste.
Issues tracked by stable code with first-seen / resolved timestamps, a DNS change timeline, and a score trend — proof of what changed and when, for you or your clients.
2026-06-08 02:00 UTC · scan #214
SPF record changed
- v=spf1 include:_spf.old-esp.example ~all
+ v=spf1 include:sendgrid.net ~all
→ alert sent: email · slack
2026-06-04 02:00 UTC · scan #210
DKIM selector s2 stopped resolving
- s2._domainkey → k=rsa; p=MIGf…
+ (no answer)
→ issue opened: dkim.selector.missing
2026-05-28 02:00 UTC · scan #203
DMARC advanced to quarantine
- v=DMARC1; p=none; rua=mailto:…
+ v=DMARC1; p=quarantine; rua=mailto:…
→ issue resolved: dmarc.policy.none
An include swapped at 02:00 — you knew by 02:01.
One lost campaign costs more than a year of watching.
$19/mo
More setup help in the ESP guides and free tools.
A scan is free and takes about five seconds.
Free, no signup. Public DNS only.
By running this scan, you agree to the Terms of Service and acknowledge the Privacy Policy.