HTML email is an email message that uses HTML and CSS for layout and styling. It enables branded designs, images, buttons, and multi-column sections. Unlike web pages, HTML email must work within strict client limitations, so it uses a different set of best practices and safer patterns.
How HTML Email Differs From Web HTML
Most HTML email relies on a constrained subset of email CSS. Many clients ignore modern CSS features, which is why styles are often applied using inline CSS. Layout often uses tables because they are widely supported. This can feel outdated to web developers, but it is a practical response to inconsistent rendering engines and security filters across inboxes.
Components That Need Special Treatment
Certain elements require email-specific techniques. Buttons are a classic example. A bulletproof button approach improves rendering in Outlook and reduces broken CTAs. Fonts often fallback, images may be blocked, and background images can be unreliable. Many teams adopt an abstraction layer like MJML to write component-style markup that compiles into email-safe HTML, reducing the chance of invalid structures and inconsistent styles.
Best Practices for Safer HTML Email Output
Keep markup simple and consistent. Use tested patterns for spacing and columns, and avoid deeply nested tables unless necessary. Validate HTML, test in major clients, and keep total size manageable. Write meaningful alt text and plan for image-off inboxes. If you allow users to edit templates, apply guardrails so they cannot introduce unsupported HTML, CSS, or nesting patterns that increase rendering risk.
A practical shortcut is to maintain a small set of proven layout patterns and reuse them. When layout rules are consistent, testing is faster and the risk of client-specific breakage drops.
HTML Email and Topol
Topol supports HTML email creation with structured building blocks that produce predictable, email-safe markup, which helps teams ship designs faster without breaking client compatibility. Learn more at Topol, create an account at Topol signup, or explore the Topol glossary.