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Notes on email authentication
Practical articles on DMARC, SPF, DKIM, MTA-STS and email deliverability from the DMARCHub Team.
Email authentication fundamentals · 25 August 2026 · 8 min read
DMARC alignment explained: SPF and DKIM alignment in practice
SPF passed, DKIM passed, and DMARC still failed. The missing piece is identifier alignment: DMARC only counts a pass when the domain that passed matches the domain in the From header. This guide explains how SPF and DKIM alignment actually work, the difference between relaxed and strict modes, and how to fix the misalignment you find in your reports.
Email authentication fundamentals · 11 August 2026 · 9 min read
SPF, DKIM and DMARC: how email authentication works together
SPF, DKIM and DMARC are often described as three separate checks, but they only make sense as one system. This guide walks through what each protocol verifies, what DMARC adds on top, and follows a single message through the full evaluation from connection to inbox.
Email authentication fundamentals · 11 August 2026 · 8 min read
What is DKIM? DomainKeys Identified Mail explained
DKIM lets a receiving mail server prove that a message really came from your domain and was not altered in transit. Here is how signatures, selectors and public keys in DNS fit together, why DKIM usually survives forwarding when SPF does not, and why you still need DMARC on top.
Email authentication fundamentals · 11 August 2026 · 8 min read
What is SPF? Sender Policy Framework explained
SPF lets a domain publish the mail servers allowed to send on its behalf, and lets receivers check each message against that list. Here is how the check actually works, which address it inspects, why forwarding breaks it, and why SPF on its own does not stop spoofing.
Email authentication fundamentals · 11 August 2026 · 9 min read
What is DMARC? A complete guide
DMARC lets you tell the world's mailbox providers what to do with email that pretends to come from your domain, and sends you reports showing who is really using it. This guide explains how DMARC builds on SPF and DKIM, what a policy actually does, and how to start protecting your domain.