Tagged “dnssec”
9 articles
DNSSEC and email security: what it does and does not do
DNSSEC turns up in almost every conversation about hardening email, usually as a vague recommendation: "you should enable DNSSEC". The advice is rarely wrong, but it is almost never explained.
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Email transport security: STARTTLS, MTA-STS, DANE
DMARC proves who sent a message, but it does nothing to protect that message while it crosses the internet. Here is how opportunistic STARTTLS, MTA-STS, DANE and TLS-RPT work together to keep inbound mail encrypted in transit, why STARTTLS alone is trivially downgraded, and the safe order to deploy enforcement without bouncing legitimate mail.
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How to fix SPF PermError
SPF PermError means a receiver tried to evaluate your SPF record and gave up, so SPF stops counting towards DMARC. This guide diagnoses PermError, TempError and the ten-lookup limit, then walks through a step by step repair process.
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DANE and TLSA records explained
DANE pins your mail server's certificate in DNSSEC-signed TLSA records so senders refuse to deliver over a downgraded or substituted TLS connection. Here is how TLSA records work, how DNSSEC anchors the trust, how DANE compares with MTA-STS, and which one fits your domain.
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What is MTA-STS and how does it work?
MTA-STS forces encrypted, authenticated delivery of your inbound mail. Learn how the _mta-sts DNS record and the HTTPS-hosted policy file work together, the difference between testing and enforce mode, and exactly how it stops TLS downgrade and interception attacks.
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What is TLS-RPT?
TLS-RPT (SMTP TLS Reporting) is a single safe-to-publish DNS record that gives you a daily, machine-readable summary of how other mail servers negotiated encryption with your inbound MX hosts. Learn what the record and its JSON reports contain, how to decode each failure type, and the exact publish-then-enforce workflow that pairs it with MTA-STS without risking an email outage.
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Fix: SPF TempError
An SPF TempError is a transient DNS failure, not a broken record. Here is what it means, why it differs from PermError, how Google, Yahoo and Microsoft treat it under SPF and DMARC, and the concrete steps that make your SPF resolution reliable.
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MTA-STS vs DANE: which transport security to use
MTA-STS and DANE both stop SMTP downgrade attacks, but they anchor trust in opposite places: the web PKI versus DNSSEC. Here is how their trust models, failure behaviour and deployment burden differ, and a concrete guide to choosing one or running both.
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RFC 8461: the MTA-STS standard explained
A precise walk through RFC 8461: why server-to-server mail needed MTA-STS, the _mta-sts DNS signal, the HTTPS-hosted policy file, the none, testing and enforce modes, and exactly how a sending MTA fetches and applies a policy.
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