Building for inboxes is not like building for browsers
Gmail strips stylesheets. Dark mode behaves differently than the web. Layout techniques that work everywhere else need workarounds here. Deep dives on the parts that actually trip you up.
Multi-column layouts
Even inlined flexbox is unreliable in Gmail. Side-by-side content in email still requires HTML tables and pixel math.
CSS inlining
Gmail's <style> support is partial and conditional. The only style that always renders lives in a style attribute on the element itself.
Outlook and MSO rendering
Classic Outlook's Word engine ignores border-radius, background images, and dark mode. Includes VML buttons.
Charts and dynamic images
Canvas and inline SVG don't survive email clients. Server-rendered PNG embedded as an <img> is the only universal option.
The Outlook 2026 deadline myth
"Retiring October 2026" is repeated everywhere. Microsoft's own roadmap says classic Outlook is supported until at least 2029.
Dark mode
You ship two palettes. Apple honors your dark one, Outlook repaints your light one, and Gmail recolors it with an undocumented algorithm.
One-click unsubscribe (RFC 8058)
Gmail and Yahoo require it for bulk senders now. A syntactically valid unsubscribe link can still fail compliance.
Link prefetching and security scanners
Corporate scanners GET every link before the reader clicks, quietly consuming single-use tokens. Magic links and verification links then fail for reasons that look impossible to reproduce.
Open and click tracking
An open is an image request and a click is a redirect hop. Apple prefetches the first, scanners traverse the second, and click-to-open divides one wrong number by another.
More coming soon
Web fonts, accessibility, background images, and more.