CSS property · data last changed 10 Nov 2026

rgba in email clients

Works in 12 of 21. Not supported in Outlook Classic. Partial in Gmail, Gmail Android, Gmail iOS and 4 more. Untested in Superhuman.

Your reader in Outlook Classic sees the email without rgba, even if it looks right where you tested it.

caniemail (MIT) via @emailens/engine 0.18.22

What to do instead in Outlook Classic

Use the comma syntax only, never the space syntax: one stray rgb(0 0 0 / 50%) can cost you every style in the <style> block in Gmail. For Outlook Classic, declare a solid hex colour first and the rgba() value after it, as in background-color:#4d4d4d; background-color:rgba(0,0,0,0.7);, so the clients that cannot read rgba() keep the solid one.

There is no drop-in fix for rgba in Outlook Classic. Design so the email still reads without it.

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rgba is not among the 24 features we have screenshotted on real installs. The ones we have →

All 21 clients, problems first

Client	Support
Outlook Classic	Not supported
Gmail	Partial ^{See caveat 1}
Gmail Android	Partial ^{See caveat 1}
Gmail iOS	Partial ^{See caveat 1}
Yahoo Mail	Partial ^{See caveat 2}
Yahoo Mail Android	Partial ^{See caveat 2}
Yahoo Mail iOS	Partial ^{See caveat 2}
AOL Mail	Partial ^{See caveat 2}
Superhuman	Untested

Works in 12: Outlook 365, Outlook (New), Outlook iOS and 9 more. Show all

Client	Support
Outlook 365	Works
Outlook (New)	Works
Outlook iOS	Works
Outlook Android	Works
Outlook for Mac	Works
Apple Mail	Works
Apple Mail iOS	Works
Samsung Mail	Works
Thunderbird	Works
HEY Mail	Works
Proton Mail	Works
Fastmail	Works

Caveats (2)

1. Gmail, Gmail Android, Gmail iOS: Whitespace syntax is not supported (rgb(0 128 0 / 1)). whitespace syntax (rgba(0 128 0 / 1)): when used in the style attribute of an element, the whole attribute is stripped. When used inside <style>, the whole <style> block is stripped.
2. Yahoo Mail, Yahoo Mail Android, Yahoo Mail iOS, AOL Mail: Whitespace syntax is not supported (rgb(0 128 0 / 1)).

Caveats as recorded by caniemail (MIT), one entry per wording.

How rgba behaves

rgba() gives a colour an alpha channel, for translucent overlays and softer borders. Most clients support the classic comma syntax, rgba(0, 0, 0, 0.5). Two things break it: Outlook Classic does not support rgba() at all, and Gmail rejects the modern space syntax, rgb(0 128 0 / 0.5), so harshly that it deletes far more than the colour.

Outlook Classic does not support rgba().
In Gmail, the space syntax rgb(0 128 0 / 1) in a style attribute removes the whole attribute, and in a <style> block it removes the whole block.
Yahoo Mail and AOL do not support the space syntax either.

Questions

Why did Gmail remove all my styles?

A colour written in the space syntax, such as rgb(0 0 0 / 50%), makes Gmail drop the whole <style> block, or the whole style attribute when it is inline. Write rgba(0,0,0,0.5) instead.

Does rgba work in Outlook?

Not in Outlook Classic. Declare a hex colour before the rgba() value so it has a solid fallback. The other Outlooks support rgba().

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