How many email clients support box-shadow?

It works in 14 of 21, partial in 2, not supported in 5.

Does box-shadow work in Fastmail?

box-shadow works in Fastmail. Closest to HEY Mail: Fastmail, which agrees on 173 of the 235 features both are tested on.

box-shadow in HEY Mail

Works box-shadow works in HEY Mail.

Works in 14 of 21 · partial in 2 · not supported in 5

Which clients

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

The fix for the clients that need it

Needed in 7 of 21: Gmail, Outlook Classic, Yahoo Mail Android and 4 more.

Use border as a fallback for box-shadow

instead

5 lines

.card {
  border: 1px solid #e0e0e0;
  /* box-shadow as progressive enhancement */
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.15);
}

Show the original

before

3 lines

.card {
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.15);
}

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Every feature in HEY Mail · box-shadow in every client

Questions

How many email clients support box-shadow?: It works in 14 of 21, partial in 2, not supported in 5.
Does box-shadow work in Fastmail?: box-shadow works 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 11 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