How many email clients support gap?

It works in 7 of 21, partial in 9, not supported in 5.

Does gap work in Fastmail?

gap is partly supported in Fastmail. Closest to HEY Mail: Fastmail, which agrees on 173 of the 235 features both are tested on.

gap in HEY Mail

Works gap works in HEY Mail.

Works in 7 of 21 · partial in 9 · not supported in 5

Which clients

Works: Apple Mail, Apple Mail iOS, Samsung Mail, Thunderbird, HEY Mail, Proton Mail, Superhuman
Partial: Gmail, Gmail Android, Gmail iOS, Outlook 365, Outlook (New), Outlook iOS, Outlook Android, Outlook for Mac, Fastmail
Not supported: Outlook Classic, Yahoo Mail, Yahoo Mail Android, Yahoo Mail iOS, AOL Mail

The fix for the clients that need it

Needed in 14 of 21: Outlook Classic, Yahoo Mail, Yahoo Mail Android and 11 more.

Use padding or margin on child elements instead of gap

instead

8 lines

<table role="presentation" cellpadding="0"
  cellspacing="0" border="0">
  <tr>
    <td style="padding-right: 16px;">Item 1</td>
    <td style="padding-right: 16px;">Item 2</td>
    <td>Item 3</td>
  </tr>
</table>

Show the original

before

5 lines

<div style="display: flex; gap: 16px;">
  <div>Item 1</div>
  <div>Item 2</div>
  <div>Item 3</div>
</div>

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Every feature in HEY Mail · gap in every client

Questions

How many email clients support gap?: It works in 7 of 21, partial in 9, not supported in 5.
Does gap work in Fastmail?: gap is partly supported 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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caniemail (MIT) via @emailens/engine 0.18.22 · tested upstream 28 Dec 2022 · data last changed 10 Nov 2026 · Outlook (New) cells are the engine's mapping