CSS Properties

text-underline-position

CSS property · 7 supported, 4 partial, 7 unsupported across 21 clients

As of Sep 2, 2026, text-underline-position fails or degrades in 14 of 21 email clients, treat it as progressive enhancement, never structure.

3/7 webmail, 1/6 desktop, 3/8 mobile clients support text-underline-position fully.
Unsupported in Outlook (New), Outlook Classic, Outlook for Mac, Yahoo Mail and 3 more.
Partial in Gmail iOS, Outlook iOS, Apple Mail, Apple Mail iOS, behavior differs from browsers, test before relying on it.
Outlook Classic (Word engine, supported to at least 2029) does not fully support text-underline-position, 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 Dec 8, 2023, synced by Emailens Sep 2, 2026.

Client Support

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

Documented caveats (1)

1.Gmail iOS, Outlook iOS, Apple Mail, Apple Mail iOS: Partial. Supports under but not right and left

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

Client-by-client behaviour for text-underline-position

Fully supports text-underline-position (7): Gmail, Gmail Android, Outlook 365, Outlook Android, Samsung Mail, Thunderbird, Proton Mail.

Partial support (4): Gmail iOS, Outlook iOS, Apple Mail, Apple Mail iOS. Expect rendering quirks unique to each engine. Partial support typically means a subset of values, an ignored shorthand, or sanitizer-specific rewrites.

No support (7): Outlook (New), Outlook Classic, Outlook for Mac, Yahoo Mail, Yahoo Mail Android, Yahoo Mail iOS, AOL Mail. Plan fallbacks for these clients before relying on text-underline-position in production sends.

Behaviour unverified in: HEY Mail, Fastmail, Superhuman.