Why It Matters
HTML emails let you create branded, visually appealing messages that plain text simply can't match. You can include call-to-action buttons, product images, formatted layouts, and consistent brand styling. But here's the tradeoff: HTML email development is stuck in the early 2000s. You're essentially writing code for Internet Explorer 6 — tables for layout, inline styles, and constant cross-client testing.
How It Works
HTML emails use a subset of HTML and CSS that email clients can render. The layout is typically built with nested tables (not divs or flexbox) because Outlook's rendering engine doesn't support modern CSS layout. Styles are written inline because many clients strip <style> blocks. Images need absolute URLs pointing to a hosted server. And you always need a plain-text fallback version for clients that can't or won't render HTML.
Quick Tips
- Keep your email width under 600px — it renders well on desktop and doesn't require horizontal scrolling on mobile
- Use table-based layouts; Outlook (still used by 7–10% of recipients) renders with Microsoft Word's engine and ignores CSS grid and flexbox
- Always include a plain-text version; some recipients prefer it, and spam filters view HTML-only emails with suspicion