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Does CSS border-inline & border-block Work in HTML Email?
Support for the `border-inline` and `border-block` shorthand properties.
Quick Answer
Does border-inline & border-block work in HTML email?
The CSS border-inline & border-block property is supported in Apple Mail, ProtonMail. It is NOT supported in Gmail, Outlook (Windows), Outlook (Mac / Web), and others. Always include a safe fallback for unsupported clients.
Which Email Clients Support CSS border-inline & border-block?
CSS support for border-inline & border-block across email clients
| Email Client | Desktop | Mobile / Web | Notes |
|---|---|---|---|
| Gmail | ✗ No | ✗ No | — |
| Outlook (Windows) | ✗ No | ? | — |
| Outlook (Mac / Web) | ✗ No | ✗ No | — |
| Apple Mail | ✓ Yes | ✓ Yes | — |
| Yahoo! Mail | ✗ No | ✗ No | — |
| Samsung Email | ? | ✗ No | — |
| Thunderbird | ? | ? | — |
| ProtonMail | ✓ Yes | ✓ Yes | — |
| Fastmail | ? | ? | — |
Frequently Asked Questions
Related CSS Properties
Test Your Email Now
Paste your HTML and see how it renders in clients that don't support border-inline & border-block.