border-spacing

Client-by-client behaviour for border-spacing

Fully supports border-spacing (12): Gmail, Gmail Android, Gmail iOS, Outlook 365, Outlook iOS, Outlook Android, Apple Mail, Apple Mail iOS, Yahoo Mail, Samsung Mail, Thunderbird, Superhuman.

No support (2): Outlook (New), Outlook Classic. Plan fallbacks for these clients before relying on border-spacing in production sends.

Behaviour unverified in: HEY Mail.

Fixes & Workarounds

<table style="border-spacing: 8px; border-collapse: separate;">
  <tr><td>Cell</td></tr>
</table>

<table cellspacing="8" style="border-collapse: separate;">
  <tr><td>Cell</td></tr>
</table>

<table style="border-spacing: 8px; border-collapse: separate;">
  <tr><td>Cell</td></tr>
</table>

<table cellspacing="8" style="border-collapse: separate;">
  <tr><td>Cell</td></tr>
</table>

Production guidance for border-spacing

border-spacing is a CSS property. Across the email client matrix, 12 of 15 tracked clients support it fully, 0 only partially, and 2 not at all. The clients most likely to require a workaround for this feature are Outlook (New), Outlook Classic. 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 border-spacing 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.