@import
CSS at-rule · 6 supported, 0 partial, 15 unsupported across 21 clients
As of Sep 2, 2026, @import fails or degrades in 15 of 21 email clients, treat it as progressive enhancement, never structure.
- 1/7 webmail, 4/6 desktop, 1/8 mobile clients support @import fully.
- Unsupported in Gmail, Gmail Android, Gmail iOS, Outlook 365 and 11 more.
- 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 Feb 28, 2019, 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 | Supported |
| Outlook Classic | desktop | Microsoft Word | Supported |
| 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 | Unsupported |
| Yahoo Mail Android | mobile | Yahoo | Unsupported |
| Yahoo Mail iOS | mobile | Yahoo | Unsupported |
| Samsung Mail | mobile | Samsung | Unsupported |
| Thunderbird | desktop | Gecko | Unsupported |
| HEY Mail | webmail | WebKit | Supported |
| Proton Mail | webmail | Proton | Unsupported |
| AOL Mail | webmail | AOL | Unsupported |
| Fastmail | webmail | Fastmail | Unsupported |
| Superhuman | desktop | Blink | Unsupported |
Client-by-client behaviour for @import
Fully supports @import (6): Outlook (New), Outlook Classic, Outlook for Mac, Apple Mail, Apple Mail iOS, HEY Mail.
No support (15): Gmail, Gmail Android, Gmail iOS, Outlook 365, Outlook iOS, Outlook Android, Yahoo Mail, Yahoo Mail Android, Yahoo Mail iOS, Samsung Mail, Thunderbird, Proton Mail, AOL Mail, Fastmail, Superhuman. Plan fallbacks for these clients before relying on @import in production sends.
Fixes & Workarounds
Gmail
Unsupported`@import` is not supported in this email client.
Gmail Android
Unsupported`@import` is not supported in this email client.
Gmail iOS
Unsupported`@import` is not supported in this email client.
Outlook 365
Unsupported`@import` is not supported in this email client.
Outlook iOS
Unsupported`@import` is not supported in this email client.
Outlook Android
Unsupported`@import` is not supported in this email client.
Yahoo Mail
Unsupported`@import` is not supported in this email client.
Yahoo Mail Android
Unsupported`@import` is not supported in this email client.
Yahoo Mail iOS
Unsupported`@import` is not supported in this email client.
Samsung Mail
Unsupported`@import` is not supported in this email client.
Thunderbird
Unsupported`@import` is not supported in this email client.
Proton Mail
Unsupported`@import` is not supported in this email client.
AOL Mail
Unsupported`@import` is not supported in this email client.
Fastmail
Unsupported`@import` is not supported in this email client.
Superhuman
Unsupported`@import` is not supported in this email client.
Related Features
Check your own HTML for @import
Paste your own, or run the sample below. Analyzed in this page, with no signup and nothing stored.
Test your @import layout across 21 email clients
Preview rendering, catch CSS issues, and see how @import displays across Outlook, Gmail, and Apple Mail. Free, no account needed.
Instant live preview · No signup required · 21 email engines
Last tested upstream: · Last synced by Emailens:
caniemail.com (MIT) records Feb 28, 2019 as the last time @import was tested in a real client, 7 years before this sync. Syncing copies that result forward, it does not re-test it. Carried in @emailens/engine data v0.12.2.