Who this applies to#
- Check compatibility whenever HTML, images, fonts, or interactive behavior affect whether a recipient can understand and act on the message
What Email client compatibility requires#
- Test the message in the clients that matter to the audience and preserve a readable fallback when a client changes or removes formatting
Outlook
Outlook message handling can expose format-specific differences
Gmail
Gmail can ask a recipient before displaying external images when it considers them suspicious
What this does not require#
- Compatibility does not require pixel-identical rendering in every client; it requires the same content and usable action
Common mistakes#
- Checking only a browser preview
- Treating visual differences as delivery failures
- Removing fallbacks to preserve a decorative effect
Email client compatibility checklist#
- Identify priority clients
- Check reading order
- Check links and buttons
- Check images-off behavior
- Keep a plain fallback