border-inline
CSS property · 3 supported, 0 partial, 14 unsupported across 21 clients
As of Sep 2, 2026, border-inline fails or degrades in 18 of 21 email clients, treat it as progressive enhancement, never structure.
- 1/7 webmail, 1/6 desktop, 1/8 mobile clients support border-inline fully.
- Unsupported in Gmail, Gmail Android, Gmail iOS, Outlook 365 and 10 more.
- Outlook Classic (Word engine, supported to at least 2029) does not fully support border-inline, 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 Jul 13, 2022, 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 | 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 | Unknown |
| HEY Mail | webmail | WebKit | Unknown |
| Proton Mail | webmail | Proton | Supported |
| AOL Mail | webmail | AOL | Unsupported |
| Fastmail | webmail | Fastmail | Unknown |
| Superhuman | desktop | Blink | Unknown |
Client-by-client behaviour for border-inline
Fully supports border-inline (3): Apple Mail, Apple Mail iOS, Proton Mail.
No support (14): 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, Samsung Mail, AOL Mail. Plan fallbacks for these clients before relying on border-inline in production sends.
Behaviour unverified in: Thunderbird, HEY Mail, Fastmail, Superhuman.
Fixes & Workarounds
Gmail
Unsupported"border-inline" is not supported in this email client.
Gmail Android
Unsupported"border-inline" is not supported in this email client.
Gmail iOS
Unsupported"border-inline" is not supported in this email client.
Outlook 365
Unsupported"border-inline" is not supported in this email client.
Outlook (New)
Unsupported"border-inline" is not supported in this email client.
Outlook Classic
Unsupported"border-inline" is not supported in this email client.
Outlook iOS
Unsupported"border-inline" is not supported in this email client.
Outlook Android
Unsupported"border-inline" is not supported in this email client.
Outlook for Mac
Unsupported"border-inline" is not supported in this email client.
Yahoo Mail
Unsupported"border-inline" is not supported in this email client.
Yahoo Mail Android
Unsupported"border-inline" is not supported in this email client.
Yahoo Mail iOS
Unsupported"border-inline" is not supported in this email client.
Samsung Mail
Unsupported"border-inline" is not supported in this email client.
AOL Mail
Unsupported"border-inline" is not supported in this email client.
Related Features
Check your own HTML for border-inline
Paste your own, or run the sample below. Analyzed in this page, with no signup and nothing stored.
Test your border-inline layout across 21 email clients
Preview rendering, catch CSS issues, and see how border-inline 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 Jul 13, 2022 as the last time border-inline was tested in a real client, 4 years before this sync. Syncing copies that result forward, it does not re-test it. Carried in @emailens/engine data v0.12.2.