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Reference · Glossary

MTA-STS

SMTP MTA Strict Transport Security (RFC 8461)

Definition

A published policy asking other mail servers to deliver to your domain only over an encrypted, verified connection.

In plain words

It is a TXT record at _mta-sts and a small policy file on a web address at mta-sts. under your domain. Its mode is testing, enforce or none.

Why it matters to a firm

Without it, mail to your firm can be delivered in the clear if someone on the path interferes with the encrypted connection.

The check behind the finding

nslookup -type=txt _mta-sts.yourfirm.ca

A record starting v=STSv1 means a policy is published.

The outside watch for your firm: see what is open before anyone else does, with the proof for the lead finding. Check my firm →