Email playbook

An email playbook for any app or business that sends email, from password resets to newsletters. It covers the message itself, the sending domain, delivery, unsubscribing, layout, privacy, security and automation.

Every rule rests on the standards that mailbox providers enforce, such as the RFCs and the sender rules of Gmail, Yahoo and Microsoft. Each one has a check you can run, often a DNS lookup, a header to read or a test send.

Start with Sending domain and authentication. Without SPF, DKIM and DMARC, large providers reject bulk mail outright.

Chapters

1. Message basics

   Build every message to the internet standards, with the right headers, a plain-text part, UTF-8, a declared language and a size inboxes accept.

   • Required 5
   • Recommended 3

2. Sending domain and authentication

   Prove each message is yours with SPF, DKIM and DMARC on aligned domains, and send it over checked TLS, or large inboxes reject it.

   • Required 6
   • Optional 3

3. Deliverability

   Reach the inbox by meeting the big providers' sender rules, keeping complaints low, separating mail streams and sending only to people who asked.

   • Required 4
   • Recommended 4

4. Unsubscribe and bounces

   Let people leave with one click and honour it within two days. Treat bounces and complaints as orders to stop, and retry only temporary errors.

   • Required 8
   • Recommended 1
   • Optional 1

5. Layout and accessibility

   Build email that every client can show and every reader can use. Semantic HTML, live text, clear contrast, small files and a test send to each major client.

   • Required 8
   • Recommended 4

6. Email privacy

   Send only what the message needs and track as little as you can. Opens are not reliable, so ask first, keep proof of consent and keep logs lean.

   • Required 5
   • Recommended 1

7. Email security

   Keep attackers away from your recipients and readers. Send safe links, single-use sign-in links and no secrets, scripts or risky files, and resist phishing.

   • Required 5
   • Recommended 1
   • Optional 1
   • Avoid 1

8. Automation and agents

   Make email that machines can use. Correct calendar invites, structured order data, honest automated mail and messages AI assistants can read safely.

   • Required 3
   • Recommended 2
   • Optional 1

All 67 rules on one page