MTA-STS Checker
Ensure your MTA-STS DNS record and policy file are properly configured.
MTA-STS Checker
Validate the Mail Transfer Agent Strict Transport Security (MTA-STS) configuration for a domain to ensure secure email transit.
Enter a domain above to instantly audit its MTA-STS DNS records and policy file.
What is MTA-STS?
MTA-STS (Mail Transfer Agent Strict Transport Security) is an email security standard that forces sending servers to encrypt emails sent to your domain via TLS. It prevents man-in-the-middle attacks where an attacker might strip away the encryption and read or alter the emails in transit.
How it works
- DNS Record: A TXT record at
_mta-sts.yourdomain.comsignals to senders that you support MTA-STS. It includes anidtag that acts as a version number. - Policy File: Senders then fetch an HTTPS text file from
https://mta-sts.yourdomain.com/.well-known/mta-sts.txt. This file defines whether encryption is enforced or just being tested, and lists the authorized MX servers.
By enforcing this standard, any emails that cannot be delivered over a secure TLS connection to the specified servers will not be delivered.
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