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border-spacing in HEY Mail

Untested caniemail has no record for border-spacing in HEY Mail.

Works in 17 of 21 · not supported in 2 · 2 untested

Which clients
Works
Gmail, Gmail Android, Gmail iOS, Outlook 365, Outlook (New), 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
Not supported
Outlook Classic, Outlook for Mac
Untested
HEY Mail, Fastmail

What to do instead in HEY Mail

Use the cellspacing HTML attribute instead of border-spacing CSS

instead 
<table cellspacing="8" style="border-collapse: separate;">
  <tr><td>Cell</td></tr>
</table>
Show the original
before 
<table style="border-spacing: 8px; border-collapse: separate;">
  <tr><td>Cell</td></tr>
</table>

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Your next question

Every feature in HEY Mail · border-spacing in every client

Questions

How many email clients support border-spacing?
It works in 17 of 21, not supported in Outlook Classic and Outlook for Mac, 2 untested.
What do I use instead of border-spacing in HEY Mail?
Use the cellspacing HTML attribute instead of border-spacing CSS.
Does border-spacing work in Fastmail?
caniemail has no record for border-spacing in Fastmail. Closest to HEY Mail: Fastmail, which agrees on 173 of the 235 features both are tested on.

To see what in your email HEY Mail does not support, paste the whole email.

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Real captures 14 Oct 2026 on 10 installs · caniemail (MIT) via @emailens/engine 0.18.22 · tested upstream 20 Dec 2023 · data last changed 10 Nov 2026 · Outlook (New) cells are the engine's mapping