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@font-face in Thunderbird

Works @font-face works in Thunderbird.

Works in 6 of 21 · not supported in 15

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

The fix for the clients that need it

Needed in 15 of 21: Gmail, Gmail Android, Gmail iOS and 12 more.

Add web-safe font fallback stack

instead
/* Keep @font-face for clients that support it */
@font-face {
  font-family: 'CustomFont';
  src: url('custom.woff2') format('woff2');
}
h1 {
  font-family: 'CustomFont', Arial, Helvetica, sans-serif;
}
Show the original
before
@font-face {
  font-family: 'CustomFont';
  src: url('custom.woff2') format('woff2');
}
h1 { font-family: 'CustomFont'; }

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Your next question

Every feature in Thunderbird · @font-face in every client

Questions

How many email clients support @font-face?
It works in 6 of 21, not supported in 15.
Does @font-face work in Apple Mail?
@font-face works in Apple Mail. Closest to Thunderbird: Apple Mail, which agrees on 219 of the 261 features both are tested on.

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

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caniemail (MIT) via @emailens/engine 0.18.22 · tested upstream 19 Dec 2023 · data last changed 10 Nov 2026 · Outlook (New) cells are the engine's mapping