AI can draft an HTML email, but it cannot guarantee that the message will render the same way in every inbox. Gmail may ignore unsupported CSS, and legacy Outlook for Windows uses Microsoft Word to render messages, with limited CSS support. Treat the generated code as a first draft: the email works only after you inspect it in the clients your audience uses and keep its content understandable when images or styling fail.
Start with a brief, not a request for code
Before prompting an AI tool, define what the message needs to say and what the reader should do. A focused brief prevents the model from filling gaps with invented copy, offers, or brand details. Keep content separate from presentation so the message still makes sense if images do not load.
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- Purpose and audience: describe who will receive the email and its single primary action.
- Copy: provide the subject line, preheader, body text, and any required legal or service language.
- Brand assets: give approved colors, allowed fonts, logo and image URLs, and useful alt text for each image.
- Action: specify the exact CTA wording and destination URL.
- Format and delivery limits: state the approximate message width, target clients and devices, and any template or sending-platform requirements.
- Uncertainties: tell the AI to list missing information rather than assume it.
Be specific about clients. “Works in email” is not a testable target; “check Gmail web and mobile, Apple Mail on iOS, and legacy Outlook for Windows” is.
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Ask for conservative email markup
For broad compatibility, request a simple table-based outer layout and inline CSS for essential styling. Ask for explicit image dimensions, meaningful alt text, readable fallback colors, and restrained responsive enhancements. Essential information should not depend on JavaScript or modern web-only layout features: email clients support different subsets of HTML and CSS, and unsupported properties may be ignored. Gmail documents its CSS support limits, while the NSW Government Email Toolkit advises table layouts, inline styles, graceful degradation, and Outlook-specific fallbacks where needed (Google’s Gmail CSS guidance; NSW Government Email Toolkit).
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Ask the AI to return the HTML, a plain-text alternative, and a short list of assumptions or risky choices. That explanation helps you review the result; it is not evidence that the code has been tested.
A prompt you can adapt
Replace the example details with your own, and supply real approved assets and destinations:
Create a conservative HTML email for [audience] whose one main action is [action]. Use this copy: [paste approved copy]. Subject: [subject]. Preheader: [preheader]. Use only these brand colors and fonts: [details]. Use these image URLs and alt text: [details]. Link the CTA to [exact destination]. The email will be sent through [platform/template constraints] and should be checked in [target email clients and devices]. Return table-based email HTML with inline essential styles, explicit image dimensions, useful alt text, a plain-text alternative, and restrained mobile enhancements. Do not invent assets, claims, prices, or offers. List missing inputs and risky assumptions separately.This prompt structure is a practical starting point, not a validated recipe or a rendering guarantee.
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MJML is an open-source, email-specific markup language that generates responsive HTML. It can reduce the amount of table nesting you write by hand, but it is a build tool rather than a promise that every client will display the result identically. Preview the generated HTML just as you would hand-authored markup.
Review the output before sending a preview
AI-generated code can be syntactically plausible while containing broken destinations, missing assets, or content that is only available in an image. Check the actual HTML and any version produced by your email platform.
- Confirm every link, especially the CTA, points to the intended destination.
- Check that image URLs are correct, use HTTPS, and have explicit dimensions and useful alt text.
- Make sure the message communicates its essential information as text, not only as an image.
- Inspect the mobile layout and verify that columns or buttons remain usable at narrow widths.
- Review the plain-text version for completeness and clear links.
- Remove any invented brand asset, discount, price, offer, or legal claim.
The NSW toolkit recommends HTTPS image hosting, image dimensions, inline styles, and graceful degradation. These choices reduce common failure points, but they do not replace testing in inboxes.
Check accessibility and readability deliberately
Use a meaningful heading order, descriptive links that make sense out of context, useful alt text, and text that does not rely on color or images alone. Check that text and backgrounds have sufficient contrast. Section508.gov recommends a contrast ratio of at least 4.5:1 when contrast is tested; that guidance is written for U.S. federal email, so follow the accessibility requirements that apply to your organization and audience (Section508.gov’s accessible email guidance).
In Outlook, use its built-in Accessibility Checker. Section508.gov explains: “The Accessibility Checker helps create accessible emails by identifying potential issues for people with disabilities in reading content or using the document.” Automated checks can flag issues, but they do not determine whether every link, image description, or reading order is meaningful.
Client support for accessibility features is uneven. The Email Markup Consortium’s 2026 report assessed 37 core HTML/CSS features relevant to semantic and accessible email. It recorded Gmail variants at 15/37 to 17/37 tested features and Outlook variants at 8/37 to 25/37. Those are feature-support scores in that report, not overall quality grades or percentages; the Outlook range reflects different platforms (Email Markup Consortium 2026 accessibility report).
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Preview in the inboxes your audience uses
A browser preview is not an acceptance test. Send the actual message through your sending platform to real test inboxes, or use a service that previews email across clients. The NSW toolkit identifies Outlook desktop, Gmail web and mobile, Apple Mail, Outlook.com, and Yahoo Mail as useful test targets. Prioritize the clients and devices relevant to your audience rather than assuming one rendering represents all recipients.
Inspect message width, line breaks, button appearance and clickability, image behavior when images are unavailable, mobile stacking, and dark-mode contrast. Pay particular attention to whether you are testing legacy Outlook for Windows or a newer Outlook surface; they do not share identical rendering behavior. Client versions, user settings, and preferences can also affect display.
Fix the largest visible problem first, then send a fresh test after each meaningful change. A preview service can broaden coverage: Litmus documents testing pasted HTML or a test sent from an email service provider. The NSW toolkit also names Litmus and Email on Acid for broader previews. Such services are optional and cannot guarantee how every recipient’s particular client and settings will render a message.
Keep a plain-text fallback; treat AMP as a separate case
A plain-text alternative helps readers and clients that do not display the HTML version well. Keep it accurate, readable, and consistent with the HTML message rather than leaving it as an afterthought.
AMP email has an additional requirement that does not apply to ordinary HTML email: Google requires an AMP message to include a fallback HTML or plain-text MIME part. Gmail may show that fallback when AMP cannot be displayed, including offline cases or after 30 days (Google’s AMP for Email guidance). Do not add AMP-specific complexity unless the message actually needs dynamic AMP content.
Quick Recap
A practical send-ready checklist
- The brief identifies the audience, one main action, approved copy, assets, destination, target clients, and platform constraints.
- The code uses conservative structure, inline essential styles, and does not depend on unsupported features for core content.
- Links, HTTPS images, dimensions, alt text, mobile behavior, and the text alternative have been checked.
- Accessibility and contrast have been reviewed with both automated checks and human judgment.
- The final message has been tested in relevant real inboxes or previewed across target clients, and meaningful fixes have been retested.
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