CSS At-Rules

@supports

CSS at-rule · 10 supported, 0 partial, 11 unsupported across 21 clients

10 of 21 email clients render @supports fully (Sep 2, 2026 data); it breaks outright in Gmail, Gmail Android, Gmail iOS and 8 more.

3/7 webmail, 3/6 desktop, 4/8 mobile clients support @supports fully.
Unsupported in Gmail, Gmail Android, Gmail iOS, Outlook 365 and 7 more.
Outlook Classic (Word engine, supported to at least 2029) does not fully support @supports, and its replacement changes little here; see the deprecation diff.
Across all clients, only 6 of 298 tracked HTML/CSS features render identically everywhere.

Source: caniemail.com (MIT), via the Emailens engine. Last tested upstream May 25, 2020, synced by Emailens Sep 2, 2026.

Client Support

Client	Category	Engine	Support
Gmail	webmail	Gmail Web	Unsupported
Gmail Android	mobile	Gmail Mobile	Unsupported
Gmail iOS	mobile	Gmail Mobile	Unsupported
Outlook 365	webmail	Outlook Web	Unsupported
Outlook (New)	desktop	Outlook Web	Unsupported
Outlook Classic	desktop	Microsoft Word	Unsupported
Outlook iOS	mobile	Outlook Mobile	Unsupported
Outlook Android	mobile	Outlook Mobile	Unsupported
Outlook for Mac	desktop	WebKit	Supported
Apple Mail	desktop	WebKit	Supported
Apple Mail iOS	mobile	WebKit	Supported
Yahoo Mail	webmail	Yahoo	Supported^{See caveat 1}
Yahoo Mail Android	mobile	Yahoo	Supported^{See caveat 1}
Yahoo Mail iOS	mobile	Yahoo	Supported^{See caveat 1}
Samsung Mail	mobile	Samsung	Supported
Thunderbird	desktop	Gecko	Unsupported
HEY Mail	webmail	WebKit	Supported
Proton Mail	webmail	Proton	Unsupported
AOL Mail	webmail	AOL	Supported^{See caveat 1}
Fastmail	webmail	Fastmail	Unsupported^{See caveat 2}
Superhuman	desktop	Blink	Supported

Documented caveats (2)

1.Yahoo Mail, Yahoo Mail Android, Yahoo Mail iOS, AOL Mail: Properties not supported by the client are replaced by _filtered_a inside the parenthesis.
2.Fastmail: Not supported. @supports is transformed into @media not all.

Caveats recorded by caniemail.com (MIT) and carried verbatim, one entry per wording rather than per client.

Client-by-client behaviour for @supports

Fully supports @supports (10): Outlook for Mac, Apple Mail, Apple Mail iOS, Yahoo Mail, Yahoo Mail Android, Yahoo Mail iOS, Samsung Mail, HEY Mail, AOL Mail, Superhuman.

No support (11): Gmail, Gmail Android, Gmail iOS, Outlook 365, Outlook (New), Outlook Classic, Outlook iOS, Outlook Android, Thunderbird, Proton Mail, Fastmail. Plan fallbacks for these clients before relying on @supports in production sends.