border
CSS property · 19 supported, 2 partial, 0 unsupported across 21 clients
border is safe in 19 of 21 email clients as of Sep 2, 2026, the holdouts are Outlook (New), Outlook Classic.
- 7/7 webmail, 4/6 desktop, 8/8 mobile clients support border fully.
- Partial in Outlook (New), Outlook Classic, behavior differs from browsers, test before relying on it.
- Outlook Classic (Word engine, supported to at least 2029) does not fully support border, 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 22, 2021, synced by Emailens Sep 2, 2026.
The border shorthand draws a line around an element and is widely supported, but interpretation varies between table cells, divs, and inline elements across clients. Outlook on Windows is famously aggressive about adding default 1px borders to table cells, which often surfaces as unwanted hairlines on rendered email.
Client Support
| Client | Category | Engine | Support |
|---|---|---|---|
| Gmail | webmail | Gmail Web | Supported |
| Gmail Android | mobile | Gmail Mobile | Supported |
| Gmail iOS | mobile | Gmail Mobile | Supported |
| Outlook 365 | webmail | Outlook Web | Supported |
| Outlook (New) | desktop | Outlook Web | PartialSee caveat 1 |
| Outlook Classic | desktop | Microsoft Word | PartialSee caveat 1 |
| Outlook iOS | mobile | Outlook Mobile | Supported |
| Outlook Android | mobile | Outlook Mobile | Supported |
| Outlook for Mac | desktop | WebKit | Supported |
| Apple Mail | desktop | WebKit | Supported |
| Apple Mail iOS | mobile | WebKit | Supported |
| Yahoo Mail | webmail | Yahoo | Supported |
| Yahoo Mail Android | mobile | Yahoo | Supported |
| Yahoo Mail iOS | mobile | Yahoo | Supported |
| Samsung Mail | mobile | Samsung | Supported |
| Thunderbird | desktop | Gecko | Supported |
| HEY Mail | webmail | WebKit | Supported |
| Proton Mail | webmail | Proton | Supported |
| AOL Mail | webmail | AOL | Supported |
| Fastmail | webmail | Fastmail | Supported |
| Superhuman | desktop | Blink | Supported |
Documented caveats (1)
- 1.Outlook (New), Outlook Classic: Partial. A border can not be bigger than 8px. Buggy. Unreliable if used on a
<p>or a<div>.
Caveats recorded by caniemail.com (MIT) and carried verbatim, one entry per wording rather than per client.
Client-by-client behaviour for border
Fully supports border (19): Gmail, Gmail Android, Gmail iOS, Outlook 365, Outlook iOS, Outlook Android, Outlook for Mac, Apple Mail, Apple Mail iOS, Yahoo Mail, Yahoo Mail Android, Yahoo Mail iOS, Samsung Mail, Thunderbird, HEY Mail, Proton Mail, AOL Mail, Fastmail, Superhuman.
Partial support (2): Outlook (New), Outlook Classic. Expect rendering quirks unique to each engine. Partial support typically means a subset of values, an ignored shorthand, or sanitizer-specific rewrites.
When to use border in email
- Drawing dividers between sections in a digest email by setting border-bottom on a <td>.
- Outlining promotional cards with a colored stroke that ties into brand identity.
- Highlighting CTA buttons with a contrasting border that survives image-blocking.
Rendering behaviour and edge cases
- Outlook on Windows occasionally renders an unstyled <table> with default 1px borders , explicitly set border="0" cellspacing="0" cellpadding="0" on every layout table.
- Apple Mail and Gmail support all border styles (dashed, dotted, double) but render them at slightly different pixel widths.
- border on inline elements can be stripped by Yahoo's sanitizer , use a wrapping <span> with display:inline-block when targeting Yahoo.
Recommended fallback strategy
Always reset table defaults with border="0" cellspacing="0" cellpadding="0". Apply border on <td> rather than <table> for consistent rendering. For decorative borders, prefer a colored cell background over a thin border, since cell color is more reliably preserved than 1px lines.
Fixes & Workarounds
Outlook (New)
Partial"border" is not supported in this email client.
Outlook Classic
Partial"border" is not supported in this email client.
Related Features
Check your own HTML for border
Paste your own, or run the sample below. Analyzed in this page, with no signup and nothing stored.
Test your border layout across 21 email clients
Preview rendering, catch CSS issues, and see how border 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 22, 2021 as the last time border was tested in a real client, 5 years before this sync. Syncing copies that result forward, it does not re-test it. Carried in @emailens/engine data v0.12.2.