The platform-agnostic email standard
What a good email does.
A sourced specification for every technical detail that matters: from From: and MIME to DMARC, one-click unsubscribe, accessible HTML, and dark mode. Written for humans and agents.
The whole message
Ten parts of good email
Foundations
Message format, headers, MIME, identity, and the envelope.
02 · 3 topicsAuthentication
SPF, DKIM, DMARC, transport security, and domain trust.
03 · 3 topicsDeliverability
Reputation, list quality, bounces, and inbox placement.
04 · 3 topicsAccessibility
Readable, operable messages for people of all abilities.
05 · 3 topicsRendering
HTML and CSS that survive real-world email clients.
06 · 3 topicsPrivacy
Consent, tracking, data minimisation, and respectful measurement.
07 · 3 topicsInternationalisation
Unicode, language, direction, and international addresses.
08 · 3 topicsLifecycle
Subscription, unsubscribe, complaints, retries, and expiry.
09 · 3 topicsSecurity
Injection, dangerous content, phishing resistance, and secrets.
10 · 3 topicsAutomation
Machine-readable actions, calendars, receipts, and agent use.
Principles
One contract, many clients
Standards, not folklore
Every topic cites the RFC, W3C guidance, or authoritative operator documentation behind it.
Provider-agnostic
The outcome matters. Use any ESP, MTA, framework, or template system that can meet it.
Test the delivered message
Generated source is not the result. Verify what arrives after relays, filters, and clients touch it.
Living specification
Recently changed
Derived audit checklist and Markdown download added
Initial Email Specification corpus published
MCP and A2A discovery surfaces added