MTA-STS Checker: the question this tool answers
MTA-STS Checker answers one focused troubleshooting question: MTA-STS checker. The live result is designed to tell you whether _mta-sts TXT is usable, whether policy id agrees with it, and whether mta-sts policy URL exposes a second path that can explain the symptom. A healthy result here is not an all-purpose website score; it only describes the business-email DNS and mail authentication evidence this tool owns.
- _mta-sts TXT
- policy id
- mta-sts policy URL
- mode
- mx patterns
- max_age
How to read the _mta-sts TXT, policy id and mta-sts policy URL evidence
Start with the value that directly controls the failing service, then use the other signals to confirm or challenge that interpretation. A single record or response can look correct while another hostname, IP family, redirect or mail-authentication path still fails. The tool therefore keeps the raw observed value visible and explains how the signals relate.
- _mta-sts TXT — Verify _mta-sts TXT from the public Internet and compare it with the value the responsible provider says should be live.
- Policy id — Verify policy id from the public Internet and compare it with the value the responsible provider says should be live.
- Mta-sts policy URL — Verify mta-sts policy URL from the public Internet and compare it with the value the responsible provider says should be live.
- Mode — Verify mode from the public Internet and compare it with the value the responsible provider says should be live.
- Mx patterns — Read the public MX priorities and targets, then verify that each target itself resolves. A visible MX record is not enough if its mail hostname is broken.
- Max_age — Verify max_age from the public Internet and compare it with the value the responsible provider says should be live.
Common mta-sts checker failure patterns
The most useful warnings are mismatches rather than isolated missing fields. _mta-sts TXT can be absent or stale; policy id can point somewhere different from the expected provider; and mta-sts policy URL can reveal a second path that behaves differently. If public sources disagree, first decide whether the difference comes from authoritative data, caching, a separate hostname, IPv6, or another protocol layer before editing configuration.
What to change — and what not to change
Change the smallest setting that the evidence proves is wrong. Compare the observed _mta-sts TXT with the current value supplied by the responsible provider, save the existing value, make one correction, and retest. Do not replace nameservers, delete unrelated MX/TXT records, disable TLS controls or remove IPv6 simply because MTA-STS Checker shows a warning in another layer. Broad changes can turn one isolated problem into several independent outages.
How HostWithShery runs MTA-STS Checker
The submitted public input is normalized and validated before any server-side request is made. HostWithShery then obtains _mta-sts TXT and policy id using the appropriate public DNS, HTTP, TLS or mail protocol and adds mta-sts policy URL plus mode where it materially changes the interpretation. URL-based checks are restricted to public destinations, and redirect targets are revalidated instead of being trusted automatically.
Example mta-sts checker interpretation
Example only: suppose _mta-sts TXT returns an expected value, but policy id points to an older destination while mta-sts policy URL shows a different result for another hostname or network path. The correct conclusion is not “everything is broken.” It is that one public path still disagrees with the intended business-email DNS and mail authentication configuration. The live result uses the domain you enter; this example is never presented as evidence about your site.
When a mta-sts checker result is inconclusive
This is a public-configuration diagnostic. Network filtering, private control-panel settings, split-horizon DNS, provider-internal state and transient routing conditions can limit what can be confirmed from outside the account. Public diagnostics cannot see private control-panel state, unpublished origin addresses, provider account status or split-horizon/internal DNS. If the remote service times out, blocks automated requests or hides a signal, the result stays inconclusive instead of inventing a provider or configuration. That distinction matters when the next step is a potentially disruptive DNS, SSL or mail change.
How to verify the repair
The public MX/authentication records should match the intended mail provider, required hostnames should resolve, and the relevant SPF/DKIM/DMARC check should no longer show the original failure. Repeat MTA-STS Checker after the change and compare the same _mta-sts TXT, policy id and mta-sts policy URL evidence that exposed the problem. A provider dashboard saying “saved” is not enough when the public Internet still returns the old value.
What to check next if MTA-STS Checker is healthy
If _mta-sts TXT, policy id and mta-sts policy URL now agree but the user-facing problem remains, move to the adjacent layer instead of editing the same setting repeatedly. Use the related diagnostics on this page to test the next plausible cause, and keep the previous result as evidence when escalating to a hosting, DNS or email provider.
Technical references
These primary standards and provider documents are used to verify the behavior described on this page. Provider dashboards can change, so use the current official value for tenant-specific DNS records rather than copying an example from another account.