When did HTML email become common?

HTML email went mainstream in the late 1990s, specifically between 1996 and 1997. Two key products made it happen: Hotmail launched in 1996 as one of the first major webmail services (anyone could sign up, no ISP required), and Microsoft Outlook 97 shipped with built-in HTML composition, putting formatted email in front of every office worker who upgraded Windows.

Before that, email was plain text only. MIME (introduced in 1993) made it technically possible to include formatting, but nobody had a client that could render it until Netscape Navigator 2.0 and early webmail apps started supporting HTML in their inboxes. Hotmail's free webmail made HTML email accessible to regular people, not just corporate users. Outlook 97 made it the default for business communication. By 1998, if you were sending marketing email, you were designing in HTML.

The shift wasn't universally loved. Developers and security purists argued (loudly) that HTML email was a security risk and an accessibility nightmare. They weren't entirely wrong. HTML opened the door to tracking pixels, phishing attacks that looked legitimate, and emails that rendered differently (or not at all) across clients. That tension between visual design and technical purity still exists today, though the battle's mostly over. HTML won.

Why does this history matter now? Because the problems from 1997 are still with us. Email clients still render HTML inconsistently (Outlook uses Word's rendering engine, which is why your CSS breaks). Accessibility is still an afterthought for most senders. And the tracking-versus-privacy debate that started with the first HTML campaigns is now playing out in Apple Mail Privacy Protection and Gmail's image proxy.

If you're designing email today, you're working with constraints that were set 25+ years ago. Worth checking how your templates render across clients with our free accessibility checker, or just reach out if you're stuck on a rendering bug that makes no sense ;)