<style>

Client-by-client behaviour for <style>

Fully supports <style> (10): Outlook 365, Outlook iOS, Outlook Android, Apple Mail, Apple Mail iOS, Yahoo Mail, Samsung Mail, Thunderbird, HEY Mail, Superhuman.

Partial support (5): Gmail, Gmail Android, Gmail iOS, Outlook (New), Outlook Classic. Expect rendering quirks unique to each engine — partial support typically means a subset of values, an ignored shorthand, or sanitizer-specific rewrites.

Fixes & Workarounds

<style>
  .header { background-color: #6d28d9; padding: 32px; }
  .title  { color: #fff; font-size: 24px; }
</style>
<div class="header">
  <h1 class="title">Hello</h1>
</div>

<div style="background-color: #6d28d9; padding: 32px;">
  <h1 style="color: #fff; font-size: 24px;
             font-family: Arial, sans-serif; margin: 0;">
    Hello
  </h1>
</div>

<style>
  .header { background-color: #6d28d9; padding: 32px; }
  .title  { color: #fff; font-size: 24px; }
</style>
<div class="header">
  <h1 class="title">Hello</h1>
</div>

<div style="background-color: #6d28d9; padding: 32px;">
  <h1 style="color: #fff; font-size: 24px;
             font-family: Arial, sans-serif; margin: 0;">
    Hello
  </h1>
</div>

<style>
  .header { background-color: #6d28d9; padding: 32px; }
  .title  { color: #fff; font-size: 24px; }
</style>
<div class="header">
  <h1 class="title">Hello</h1>
</div>

<div style="background-color: #6d28d9; padding: 32px;">
  <h1 style="color: #fff; font-size: 24px;
             font-family: Arial, sans-serif; margin: 0;">
    Hello
  </h1>
</div>

Production guidance for <style>

<style> is a HTML element. Across the email client matrix, 10 of 15 tracked clients support it fully, 5 only partially, and 0 not at all. The clients most likely to require a workaround for this feature are Gmail, Gmail Android, Gmail iOS. Each of them needs a tailored fallback — see the per-client examples above for the specific code fix Emailens recommends.

When in doubt, ship a baseline that renders without <style> and treat it as progressive enhancement on clients where support is verified. Emailens automatically detects cross-client divergence on this feature when you preview an email, so you can see exactly which template paths break before a campaign goes out.