CSS property · data last changed 10 Nov 2026
border in email clients
Works in 20 of 21. Partial in Outlook Classic.
Your reader in Outlook Classic may not see border the way you wrote it, even if it looks right where you tested it.
caniemail (MIT) via @emailens/engine 0.18.22
What to do instead in Outlook Classic
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.
- Partial. A border can not be bigger than 8px.
- Buggy. Unreliable if used on a
<p>or a<div>.
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border is not among the 24 features we have screenshotted on real installs. The ones we have →
All 21 clients, problems first
| Client | Support |
|---|---|
| Outlook Classic | Partial See caveat 1 |
Works in 20: Gmail, Gmail Android, Gmail iOS and 17 more. Show all
| Client | Support |
|---|---|
| Gmail | Works |
| Gmail Android | Works |
| Gmail iOS | Works |
| Outlook 365 | Works |
| Outlook (New) | Works |
| Outlook iOS | Works |
| Outlook Android | Works |
| Outlook for Mac | Works |
| Apple Mail | Works |
| Apple Mail iOS | Works |
| Yahoo Mail | Works |
| Yahoo Mail Android | Works |
| Yahoo Mail iOS | Works |
| Samsung Mail | Works |
| Thunderbird | Works |
| HEY Mail | Works |
| Proton Mail | Works |
| AOL Mail | Works |
| Fastmail | Works |
| Superhuman | Works |
Caveats (1)
- 1. Outlook Classic: Partial. A border can not be bigger than 8px. Buggy. Unreliable if used on a
<p>or a<div>.
Caveats as recorded by caniemail (MIT), one entry per wording.
How border behaves
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 Classic is famously aggressive about adding default 1px borders to table cells, which often surfaces as unwanted hairlines on rendered email.
- Outlook Classic 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.
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