How to test plain-text fallback?

Every HTML email should include a plain-text MIME part as fallback for clients that don't render HTML or users who prefer text-only viewing. To test it, configure your email client to display plain text only (most clients have this option in settings), or examine the raw MIME source of your email to inspect the text/plain section directly. Many ESPs generate plain text automatically, but auto-generation often produces poor results.

When reviewing plain-text versions, verify that content reads naturally without HTML formatting context. Auto-generated plain text often creates ugly results: navigation links become nonsensical lists, styled headings lose hierarchy, and call-to-action buttons become bare URLs. The text should flow logically, links should be displayed clearly (ideally labeled with descriptive text before the URL), and important information shouldn't be lost.

Best practice is to craft the plain-text version separately rather than relying on auto-generation. Write it as a standalone piece that delivers your message without visual design supporting it. Include full URLs where readers would expect links, use line breaks strategically for readability, and ensure nothing critical is conveyed only through HTML elements. Plain text isn't obsolete-it's a deliverability signal, an accessibility feature, and a fallback for technical failures. Treat it as a first-class version of your email.