MTA-STS

SMTP MTA Strict Transport Security (MTA-STS) is an email security standard that enables mail servers to declare their ability to receive TLS-encrypted email and specify whether sending servers should refuse to deliver to MX hosts that don't offer TLS. It prevents attackers from downgrading SMTP connections to plaintext. MTA-STS is configured via a DNS TXT record and a policy file hosted at a well-known HTTPS URL. It complements DMARC and DKIM in securing the email delivery path.

Why it matters for your website

• 1Prevents your domain from being used in phishing and spoofing attacks
• 2Required for email deliverability to Gmail, Yahoo, and major providers
• 3Missing records are flagged as high-severity findings in security audits