CSS Properties

nesting

CSS property · 2 supported, 3 partial, 13 unsupported across 21 clients

As of Sep 2, 2026, nesting fails or degrades in 19 of 21 email clients, treat it as progressive enhancement, never structure.

0/7 webmail, 1/6 desktop, 1/8 mobile clients support nesting fully.
Unsupported in Gmail, Gmail Android, Gmail iOS, Outlook 365 and 9 more.
Partial in Apple Mail, Samsung Mail, Proton Mail, behavior differs from browsers, test before relying on it.
Outlook Classic (Word engine, supported to at least 2029) does not fully support nesting, 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 Aug 31, 2023, 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	Unsupported
Apple Mail	desktop	WebKit	Partial^{See caveat 1}
Apple Mail iOS	mobile	WebKit	Supported
Yahoo Mail	webmail	Yahoo	Unsupported^{See caveat 2}
Yahoo Mail Android	mobile	Yahoo	Unsupported^{See caveat 2}
Yahoo Mail iOS	mobile	Yahoo	Unsupported^{See caveat 2}
Samsung Mail	mobile	Samsung	Partial^{See caveat 3}
Thunderbird	desktop	Gecko	Supported
HEY Mail	webmail	WebKit	Unknown
Proton Mail	webmail	Proton	Partial^{See caveat 4}
AOL Mail	webmail	AOL	Unsupported^{See caveat 2}
Fastmail	webmail	Fastmail	Unknown
Superhuman	desktop	Blink	Unknown

Documented caveats (4)

1.Apple Mail: Partial. E { F {}} doesn’t work, but E { & F {}} does. Full support was added in macOS 14.2.
2.Yahoo Mail, Yahoo Mail Android, Yahoo Mail iOS, AOL Mail: Not supported. The nested selectors are removed, making the nested properties apply to the parent selector.
3.Samsung Mail: Partial. Not supported with Hotmail/Outlook accounts.
4.Proton Mail: Partial. @media is not fully supported, and & & & syntax not supported

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

Client-by-client behaviour for nesting

Fully supports nesting (2): Apple Mail iOS, Thunderbird.

Partial support (3): Apple Mail, Samsung Mail, Proton Mail. Expect rendering quirks unique to each engine. Partial support typically means a subset of values, an ignored shorthand, or sanitizer-specific rewrites.

No support (13): 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, AOL Mail. Plan fallbacks for these clients before relying on nesting in production sends.

Behaviour unverified in: HEY Mail, Fastmail, Superhuman.