← All sixteen checks MTA-STS (Mail Transfer Agent Strict Transport Security)

MTA-STS
explained.

Overview

What is
MTA-STS?

MTA-STS enforces secure TLS connections for email transmission, preventing man-in-the-middle attacks on email delivery.

Importance

Why it
matters.

MTA-STS prevents attackers from intercepting emails in transit by forcing encrypted connections. Critical for protecting business email communications.

Risks

What can
go wrong.

If MTA-STS is not configured: email transmission can be intercepted, attackers can downgrade to unencrypted connections, and sensitive business communications are at risk.

Under the hood

Technical
details.

MTA-STS requires: 1) _mta-sts.domain.com TXT record with "v=STSv1", 2) Policy file at https://mta-sts.domain.com/.well-known/mta-sts.txt with "mode: enforce", 3) Valid SSL certificate. Mode "enforce" means strict enforcement, "testing" is monitoring only.

Take action

Check your domain’s
MTA-STS policy.

Run a free security check to see how your domain scores across all sixteen checks, including MTA-STS validation.

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