What are email design best practices?
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Picture yourself sending a campaign that looks pixel-perfect in your ESP's preview but arrives broken in Outlook, with blown-out fonts in Gmail, and a layout that requires horizontal scrolling on mobile. This is the reality of email design: unlike the web, you don't control the rendering environment. Different email clients use wildly different rendering engines, and what works in one may not work in another.
The most reliable foundation is a table-based layout with a max-width of 600px. Tables render consistently across email clients, including older versions of Outlook that ignore modern CSS. Use inline styles wherever possible, since many clients strip or ignore embedded stylesheets. Keep your design single-column for mobile, and set a font stack that degrades gracefully: a web font first, then a system font fallback like Arial or Georgia. Responsive email design means your layout adapts to the screen it's on, not just scales down clumsily.
Images need alt text, always. A significant portion of your subscribers see emails with images off by default, especially in corporate environments. If your email is 90% image with no supporting text, those readers see nothing meaningful. Use real text for your headlines and CTAs, and treat images as enhancement rather than structure. For any image you want to look good across light and dark mode, save it as a transparent PNG rather than a JPG with a white background. Dark mode can invert white backgrounds in jarring ways.
Your call-to-action should be a real HTML button, not a linked image. An HTML button renders reliably, shows up even with images disabled, and is easier to tap on mobile. Make it at least 44x44px for comfortable tapping, and keep the label to three or four words. CTA design is where design and copy intersect most directly.
So before you send anything, test it across the clients your audience actually uses. If your list skews heavily toward Outlook users, you need to see exactly how your template renders in Outlook 2019 and Microsoft 365. Testing across clients takes less time than you think and saves you from the slow embarrassment of discovering a broken layout days after a campaign goes out.
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