border-spacing

Client-by-client behaviour for border-spacing

Fully supports border-spacing (16): Gmail, Gmail Android, Gmail iOS, Outlook 365, Outlook iOS, Outlook Android, Apple Mail, Apple Mail iOS, Yahoo Mail, Yahoo Mail Android, Yahoo Mail iOS, Samsung Mail, Thunderbird, Proton Mail, AOL Mail, Superhuman.

No support (3): Outlook (New), Outlook Classic, Outlook for Mac. Plan fallbacks for these clients before relying on border-spacing in production sends.

Behaviour unverified in: HEY Mail, Fastmail.

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>

<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, 16 of 15 tracked clients support it fully, 0 only partially, and 3 not at all. The clients most likely to require a workaround for this feature are Outlook (New), Outlook Classic, Outlook for Mac. 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.