Outlook (New)
Outlook (New) replaces the deprecated Outlook Classic. See what actually changes for HTML email .
The new Outlook for Windows uses a Chromium-based web engine identical to Outlook.com/365, replacing the legacy Word rendering engine. This means dramatically better CSS support , flexbox, grid, border-radius, background images, and most modern CSS properties work correctly. Microsoft is rolling this out as the default Windows mail client.
Microsoft's replacement for classic Outlook on Windows. Uses the same web engine as Outlook.com. Being rolled out to all Windows users , classic Outlook stops being the default in April 2026 and is supported to at least 2029.
CSS coverage profile for Outlook (New)
Outlook (New) renders with the Outlook Web engine and supports 57 of 298 tracked CSS and HTML features fully, with 30 partially supported and 210 unsupported. That places it in a narrow coverage band.
Most modern CSS is unsupported. This client effectively requires a separate, table-based fallback path for any non-trivial layout.
57
Supported
30
Partial
210
Unsupported
298
Total
Key gotchas in Outlook (New)
position (absolute/fixed) Position properties are partially supported. Use table-based positioning for critical layout elements.
transform CSS transforms are stripped. Pre-render visual effects as images.
animation / transition CSS animations and transitions are removed. Use static designs.
How Outlook (New) renders email
- New Outlook on Windows shares its rendering engine with Outlook.com web, so any CSS that works in the web client should produce identical results in the desktop app , a major upgrade from the Word-based legacy client.
- CSS animations and transforms are stripped at parse time. Any motion-based brand element should be pre-rendered as a static image fallback.
- Position properties beyond static and relative are partially supported; absolute and fixed are dropped in some layouts. Keep critical visual positioning inside table cells.
- Microsoft's data-ogsc dark-mode attribute applies here as well, mirroring Outlook 365 web behaviour.
Dark mode behaviour in Outlook (New)
Outlook (New) applies partial color inversion in dark mode, similar to Outlook.com. Use [data-ogsc] or [data-ogsb] CSS attribute selectors to override dark mode color changes.
QA checklist for Outlook (New)
- Confirm that any animation or transition in the design has a sensible static fallback for New Outlook.
- Test absolute-positioned overlays , they may collapse in this client even though they work in the modern web Outlook.
- Check rendering of conditional <!--[if mso]> blocks; the new engine ignores them, which is correct behaviour but easy to overlook in mixed templates.
Related clients
Breaks here, works nearly everywhere else
44 features that Outlook (New) drops while most other clients render them. This is usually what is behind an email that looks correct everywhere but here.
- background-position 19
- background-repeat 19
- caption-side 19
- max-height 19
- min-width 19
- outline 19
- list-style-position 18
- min-height 18
- opacity 18
- background-size 17
- unit-vw 17
- display:flex 17
- display:grid 17
- border-spacing 16
- table-layout 16
- unit-vh 16
- z-index 16
- <input type="checkbox"> 15
- <input type="hidden"> 15
- <input type="radio"> 15
Renders here, dropped almost everywhere else
Safe in Outlook (New) and almost nowhere else, so it needs a fallback the moment the send is not Outlook (New)-only.
Where Outlook (New) is weakest
- CSS Properties 141
- HTML Elements 30
- Pseudo-Classes & Selectors 28
- HTML Attributes 14
- CSS At-Rules 9
Closest client: Outlook Classic
Outlook Classic agrees with Outlook (New) on 95% of verified features. They still differ on 15: <base>, [aria-hidden], [aria-label], [aria-live], [background], [height], and 9 more.
Side by side
HTML Elements48
| Feature | Support |
|---|---|
| <abbr> | Unsupported |
| <acronym> | Unsupported |
| <address> | Supported |
| <audio> | Unsupported |
| <base> | Supported |
| <bdi> | Unsupported |
| <blockquote> | Supported |
| <body> | Supported |
| <button type="reset"> | Unsupported |
| <button type="submit"> | Unsupported |
| <code> | Supported |
| <del> | Supported |
| <dfn> | Partial |
| <dialog> | Unsupported |
| <div> | Supported |
| <form> | Unsupported |
| <h1> | Supported |
| <hr> | Supported |
| <img> | Supported |
| <input type="checkbox"> | Unsupported |
| <input type="hidden"> | Unsupported |
| <input type="radio"> | Unsupported |
| <input type="reset"> | Unsupported |
| <input type="submit"> | Unsupported |
| <input type="text"> | Unsupported |
| <link> | Supported |
| <marquee> | Unsupported |
| <meter> | Unsupported |
| <object> | Unsupported |
| <p> | Supported |
| <picture> | Unsupported |
| <pre> | Supported |
| <progress> | Unsupported |
| <rp> | Unsupported |
| <rt> | Unsupported |
| <ruby> | Unsupported |
| <select> | Unsupported |
| <small> | Supported |
| <span> | Supported |
| <strike> | Supported |
| <strong> | Supported |
| <style> | Partial |
| <svg> | Unsupported |
| <table> | Supported |
| <textarea> | Unsupported |
| <ul> | Partial |
| <video> | Unsupported |
| <wbr> | Unsupported |
HTML Attributes22
| Feature | Support |
|---|---|
| [align] | Supported |
| [aria-describedby] | Unsupported |
| [aria-hidden] | Supported |
| [aria-label] | Supported |
| [aria-labelledby] | Unsupported |
| [aria-live] | Partial |
| [background] | Partial |
| [cellpadding] | Supported |
| [cellspacing] | Supported |
| [command] | Unsupported |
| [dir] | Partial |
| [height] | Partial |
| [hidden] | Unsupported |
| [lang] | Supported |
| [loading] | Unsupported |
| [popover] | Unsupported |
| [required] | Unsupported |
| [role] | Supported |
| [srcset] | Unsupported |
| [target] | Partial |
| [valign] | Supported |
| [width] | Partial |
HTML & Email Structure8
| Feature | Support |
|---|---|
| amp4email | Unsupported |
| anchor-links | Supported |
| doctype | Unsupported |
| html-comments | Supported |
| html5-semantics | Unsupported |
| image-maps | Supported |
| mailto-links | Supported |
| meta-color-scheme | Unsupported |
CSS At-Rules10
| Feature | Support |
|---|---|
| @font-face | Partial |
| @import | Supported |
| @keyframes | Unsupported |
| @media | Unsupported |
| @media device-pixel-ratio | Unsupported |
| @media hover | Unsupported |
| @media orientation | Unsupported |
| @media prefers-color-scheme | Unsupported |
| @media prefers-reduced-motion | Unsupported |
| @supports | Unsupported |
Pseudo-Elements6
| Feature | Support |
|---|---|
| ::after | Unsupported |
| ::before | Unsupported |
| ::first-letter | Unsupported |
| ::first-line | Unsupported |
| ::marker | Unsupported |
| ::placeholder | Unsupported |
Pseudo-Classes & Selectors34
| Feature | Support |
|---|---|
| :adjacent-sibling | Unsupported |
| :attribute-selector | Unsupported |
| :chaining | Unsupported |
| :checked | Unsupported |
| :child-combinator | Unsupported |
| :class-selector | Supported |
| :descendant-combinator | Supported |
| :first-child | Unsupported |
| :first-of-type | Unsupported |
| :focus | Unsupported |
| :focus-visible | Unsupported |
| :focus-within | Unsupported |
| :general-sibling | Unsupported |
| :grouping | Supported |
| :has | Unsupported |
| :hover | Unsupported |
| :id-selector | Supported |
| :lang | Unsupported |
| :last-child | Unsupported |
| :last-of-type | Unsupported |
| :link | Supported |
| :not | Unsupported |
| :nth-child | Unsupported |
| :nth-last-child | Unsupported |
| :nth-of-type | Unsupported |
| :only-child | Unsupported |
| :only-of-type | Unsupported |
| :target | Unsupported |
| :type-selector | Supported |
| :universal-selector | Unsupported |
| :visited | Unsupported |
| pseudo-class-active | Unsupported |
| pseudo-class-default | Unsupported |
| pseudo-class-nth-last-of-type | Unsupported |
CSS Functions8
| Feature | Support |
|---|---|
| calc | Unsupported |
| clamp | Unsupported |
| conic-gradient | Unsupported |
| fit-content | Unsupported |
| linear-gradient | Unsupported |
| max | Unsupported |
| min | Unsupported |
| radial-gradient | Unsupported |
CSS Properties162
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Support data last updated Sep 2, 2026 - synced from caniemail.com (MIT) via @emailens/engine.