Available at https://www.suped.com/tools/mta-sts-checker.
Enter a domain and the checker looks up the _mta-sts TXT record, fetches the policy file from the standard HTTPS location, compares live MX records to the policy, and tests whether each MX server can upgrade to an encrypted SMTP connection with STARTTLS.
How it works
Enter a domain and click Check. You can also click View sample to run the sample check for suped.com.
Results are split into three sections: the MTA-STS DNS record, the MTA-STS policy file, and MX server encryption support.
Checks
MTA-STS DNS record
- Record found at
_mta-sts - Only one MTA-STS TXT record found
- Record has valid
v=andid=tags
MTA-STS policy file
- Policy file found at the standard HTTPS URL
- Policy file is valid
- Policy file is served via HTTPS
MX server supports encryption
- MX records found
- MX servers accept SMTP and advertise STARTTLS
- MX records match the hosts listed in the policy file
In-app version
The same MTA-STS checker is available inside the app under Tools → MTA-STS checker. Use it the same way you would the public tool. Results and the share link are identical to the public version.
