Verify both components
Check the _mta-sts TXT marker and the HTTPS policy file required by the standard.
Inbound mail transport security
Verify encrypted delivery
all the way to policy.
Check both the DNS marker and the live policy file receivers use to require trusted TLS for inbound mail.
Domain not found
Check the spelling and try again.
Tracing target
Resolving public DNS
Reading address, mail, nameserver and policy records.
Try
Your connection
Detecting…
Checking IPv4
Locating network
Checking provider
What the result means
MTA-STS has two public parts
The DNS marker announces a policy version while the HTTPS file contains the enforcement mode, permitted MX patterns and cache lifetime. This checker validates both rather than treating a TXT marker alone as a working deployment.
- DNS marker and policy id
- Live HTTPS policy
- Mode, MX and max-age checks
Diagnostic field guide
Use the evidence, not the guess.
Three practical ways to use this lookup, followed by the boundary the result cannot cross.
Reviewed Sep 2026Review enforcement mode
Distinguish testing from enforce mode before relying on strict TLS delivery.
Match receiving hosts
Compare policy mx patterns with the domain's published mail exchangers.
How to read the result
- Validate the STSv1 DNS marker and note its policy id.
- Fetch the policy from the fixed well-known HTTPS location and read mode, max_age and mx lines.
- Confirm each intended mail exchanger matches a policy pattern before enabling enforce mode.
Common questions
Before you act on the result
Why does MTA-STS require DNS and HTTPS?
The TXT record signals a policy version and change id. The authenticated HTTPS file carries the actual mode, permitted MX patterns and cache lifetime.
What is the difference between testing and enforce mode?
Testing mode lets supporting senders report policy failures while still delivering. Enforce mode asks them not to deliver when the TLS or MX policy cannot be satisfied.
Choose the question
One system, fourteen focused tools.
Each tool has its own indexable page and opens the report at the evidence that answers its question.
DNSDNS lookup
Every address, mail, verification and policy record.
A · AAAA · MX · TXT · NS GLBGlobal DNSLive answers from probes across ten countries.
Answer · TTL · resolver · latency RDPWHOIS / RDAPRegistrar, dates, status and published contacts.
Registry + registrar data IPIP lookupNetwork owner, route, reverse name and region.
IPv4 + IPv6 ASNASN lookupAutonomous system, BGP prefix and RPKI state.
RIPEstat routing signals TLSSSL checkerIssuer, validity, names and fingerprint.
Live certificate check MXMX lookupReceiving servers, preference and detected mail provider.
Mail routing records MAILEmail securityComplete validation across authentication and transport.
Seven policy controls SPFSPF checkerSender policy, authorization strength and DNS-limit risks.
Policy syntax + safety DMARCDMARC checkerEnforcement, alignment, rollout and report destinations.
Anti-spoofing policy DKIMDKIM checkerSelector lookup, key presence, type and base64 form.
Public signing keys STSMTA-STS checkerDNS marker plus live HTTPS transport policy.
Encrypted inbound mail RPTTLS-RPT checkerSMTP TLS report policy and destination validation.
Transport visibility HDRSecurity headersBrowser protections from the final HTTPS response.
HSTS · CSP · framing · policyEvidence before certainty
The internet has layers.
We keep them separate.
A nameserver identifies the DNS operator. An edge address identifies a public delivery network. An ASN identifies the organization announcing a route. None automatically proves where a hidden origin application runs.
ObservedCorrelatedUnknown stays unknown
Read the detection methodology →
Field notes
Read the signal correctly.
DNS · 6 minDNS propagation is really cache expiry
Why locations disagree, what TTL controls and when to test again.
REGISTRY · 5 minWHOIS text became structured RDAPWhere registration fields come from and why some remain unpublished.
DELIVERY · 7 minAn edge address is not an originWhat public CDN and hosting signals can and cannot prove.
Agent-ready JSON
Give your script or your AI the same public evidence.
GET /api/dns?target=example.com&type=MX
Complete lookup for
example.com
Just resolved
Target
example.com
Resolves to
93.184.216.34
Announced by
Edgecast
Network location
United States
Delivery platform detected
Cloudflare is in front of this domain
These public addresses terminate at the provider's edge.
Primary IP
Not available
IPv4 address
ASNrouted
Not available
Autonomous system
NameserversNS
Not available
No NS records found
Observed status
Reachable
DNS is answering normally
IPv6
Public address
Network address
- Announced by
- Not available
- Route
- Not available
- Reverse name
- Not available
- Network region
- Not available
Every published answer
DNS records
| Type | Host | Answer | TTL |
|---|
No records in this group.
Showing 0 records
Certificate history + live DNS
Subdomains
Discovering names from certificate transparency, then checking which ones still resolve.
| Host | Live DNS chain | State | Certificate evidence |
|---|
Subdomain data unavailable
Certificate Transparency could not be reached.
Showing 0 hosts
Certificate transparency is historical evidence. “Not resolved” means the name did not return a current A/CNAME answer; it may be retired, internal, or IPv6-only.
Live answers around the world
Global DNS
Queries run on real probes in ten countries. Results may vary because of propagation, geo-routing, or resolver cache.
Worldwide resolver checkReady to probe
Not run
10
real probe locations
Run a check to see what each resolver returns.
See propagation, not a simulation.
Each row will show the probe city, network, recursive resolver, answer, TTL, and query time.
What answers on HTTPS
Web delivery
Correlated public signalsDetected stack
Confidence rises when DNS, HTTP and network evidence agree
Browser protectionsSecurity headers
Read from the final HTTPS response
Delivery and anti-spoofing
Email security
MX
Mail providerNot detectedNo MX records returned
Grade–
Policy scoreWaiting for a domainChecks distinguish valid policy from record presence.
Action items–Failures and hardening recommendations
SPFChecking sender policy
DMARCChecking anti-spoofing policy
DKIMChecking common selectors
MTA-STSChecking transport policy
TLS reportingChecking aggregate reports
BIMIChecking brand indicator
Where traffic lands
Network & hosting
AS
Announced by (BGP)Not available
- Registered to (RDAP)
- Not available
- Registry assignee
- Not available
- ASN
- Not available
- Range
- Not available
- Connection
- Not available
- Timezone
- Not available
- BGP prefix
- Not available
- RPKI route
- Not available
- Reverse DNS
- Not available
- Routing model
- Not available
- Abuse contact
- Not available
Approximate network location
Not available
IP geolocation, not a device address
Registry data
Registration
Signals worth noticing
Security posture
SSL / TLS certificate issued by
Checking certificate…
Reading certificate transparency records
Checking
Not available
Not available
Not available
Authoritative DNSChecking nameservers
Mail policyChecking SPF and DMARC
Certificate policyChecking CAA records
Allocation authority
IP registry
Registry allocation ≠ device owner
These records describe the organization responsible for the address range. They do not identify the individual using this IP.
Routing and operational checks
IP route signals
RPKI validationChecking route authorization
BGP announcementChecking the public routing table
Reverse DNSChecking PTR ownership signal
Abuse contactFinding the responsible network desk
Network roleClassifying the announcing network
Location precisionApproximate network region only