CSS Properties

align-items

CSS property · 12 supported, 0 partial, 9 unsupported across 21 clients

align-items controls cross-axis alignment of flex items. Because flexbox itself is largely unsupported in email , Outlook ignores it, Gmail strips it , align-items has equally narrow practical usefulness. Modern Apple Mail and Superhuman support it, making it a niche progressive-enhancement tool.

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	Supported
Outlook (New)	desktop	Outlook Web	Unsupported
Outlook Classic	desktop	Microsoft Word	Unsupported
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	Unsupported
Yahoo Mail Android	mobile	Yahoo	Unsupported
Yahoo Mail iOS	mobile	Yahoo	Unsupported
Samsung Mail	mobile	Samsung	Supported
Thunderbird	desktop	Gecko	Supported
HEY Mail	webmail	WebKit	Supported
Proton Mail	webmail	Proton	Supported
AOL Mail	webmail	AOL	Unsupported
Fastmail	webmail	Fastmail	Supported
Superhuman	desktop	Blink	Supported

Client-by-client behaviour for align-items

Fully supports align-items (12): Outlook 365, Outlook iOS, Outlook Android, Outlook for Mac, Apple Mail, Apple Mail iOS, Samsung Mail, Thunderbird, HEY Mail, Proton Mail, Fastmail, Superhuman.

No support (9): Gmail, Gmail Android, Gmail iOS, Outlook (New), Outlook Classic, Yahoo Mail, Yahoo Mail Android, Yahoo Mail iOS, AOL Mail. Plan fallbacks for these clients before relying on align-items in production sends.

When to use align-items in email

Vertically aligning side-by-side columns in Apple-Mail-targeted layouts.
Centering a logo with adjacent text in a flex header.
Controlled alignment in modern-client-only designs that fall back to tables elsewhere.

Rendering behaviour and edge cases

Outlook on Windows ignores all flexbox properties including align-items.
Gmail's sanitizer strips display: flex, neutralizing any align-items declaration.
Apple Mail and Superhuman honor align-items reliably when display: flex is also present.

Recommended fallback strategy

Always provide a table-based fallback for any flex layout. Use align-items only where the audience is known to skew toward modern WebKit-based clients. Inside <!--[if mso]> conditionals, supply a table layout with valign attributes for vertical alignment.