CSS Functions

max

CSS function · 5 supported, 3 partial, 6 unsupported across 15 clients

The max() CSS function returns the largest of a set of values and is used to enforce a minimum. Like min() and calc(), it is a modern function with limited email support — Outlook on Windows ignores it, while Apple Mail and modern Gmail honor it.

Client Support

Client	Category	Engine	Support
Gmail	webmail	Gmail Web	Supported
Gmail Android	mobile	Gmail Mobile	Partial
Gmail iOS	mobile	Gmail Mobile	Partial
Outlook 365	webmail	Outlook Web	Unsupported
Outlook (New)	desktop	Outlook Web	Unsupported
Outlook Classic	desktop	Microsoft Word	Unsupported
Outlook iOS	mobile	Outlook Mobile	Unsupported
Outlook Android	mobile	Outlook Mobile	Unsupported
Apple Mail	desktop	WebKit	Supported
Apple Mail iOS	mobile	WebKit	Supported
Yahoo Mail	webmail	Yahoo	Unsupported
Samsung Mail	mobile	Samsung	Partial
Thunderbird	desktop	Gecko	Supported
HEY Mail	webmail	WebKit	Supported
Superhuman	desktop	Blink	Unknown

Client-by-client behaviour for max

Fully supports max (5): Gmail, Apple Mail, Apple Mail iOS, Thunderbird, HEY Mail.

Partial support (3): Gmail Android, Gmail iOS, Samsung Mail. Expect rendering quirks unique to each engine — partial support typically means a subset of values, an ignored shorthand, or sanitizer-specific rewrites.

No support (6): Outlook 365, Outlook (New), Outlook Classic, Outlook iOS, Outlook Android, Yahoo Mail. Plan fallbacks for these clients before relying on max in production sends.

Behaviour unverified in: Superhuman.

When to use max in email

Enforcing a minimum padding regardless of fluid container size.
Ensuring a minimum font-size in fluid typography systems.
Forcing a minimum width on responsive button elements to keep them tappable on small screens.

Rendering behaviour and edge cases

Outlook on Windows ignores max() and falls back to the previous declaration.
Apple Mail supports max() across recent macOS and iOS releases.
max() expressions with mixed units behave inconsistently — prefer same-unit comparisons.

Recommended fallback strategy

Always supply a literal fallback before max() so Outlook receives a sensible default. Use max() as progressive enhancement layered on top of conservative pixel values.