The following CSS properties are supported in Gmail and Inbox:
- azimuth
- background
- background-blend-mode
- background-clip
- background-color
- background-image
- background-origin
- background-position
- background-repeat
- background-size
- border
- border-bottom
- border-bottom-color
- border-bottom-left-radius
- border-bottom-right-radius
- border-bottom-style
- border-bottom-width
- border-collapse
- border-color
- border-left
- border-left-color
- border-left-style
- border-left-width
- border-radius
- border-right
- border-right-color
- border-right-style
- border-right-width
- border-spacing
- border-style
- border-top
- border-top-color
- border-top-left-radius
- border-top-right-radius
- border-top-style
- border-top-width
- border-width
- box-sizing
- break-after
- break-before
- break-inside
- caption-side
- clear
- color
- column-count
- column-fill
- column-gap
- column-rule
- column-rule-color
- column-rule-style
- column-rule-width
- column-span
- column-width
- columns
- direction
- display
- elevation
- empty-cells
- float
- font
- font-family
- font-feature-settings
- font-kerning
- font-size
- font-size-adjust
- font-stretch
- font-style
- font-synthesis
- font-variant
- font-variant-alternates
- font-variant-caps
- font-variant-east-asian
- font-variant-ligatures
- font-variant-numeric
- font-weight
- height
- image-orientation
- image-resolution
- isolation
- letter-spacing
- line-height
- list-style
- list-style-position
- list-style-type
- margin
- margin-bottom
- margin-left
- margin-right
- margin-top
- max-height
- max-width
- min-height
- min-width
- mix-blend-mode
- object-fit
- object-position
- opacity
- outline
- outline-color
- outline-style
- outline-width
- overflow
- padding
- padding-bottom
- padding-left
- padding-right
- padding-top
- pause
- pause-after
- pause-before
- pitch
- pitch-range
- quotes
- richness
- speak
- speak-header
- speak-numeral
- speak-punctuation
- speech-rate
- stress
- table-layout
- text-align
- text-combine-upwrite
- text-decoration
- text-decoration-color
- text-decoration-line
- text-decoration-skip
- text-decoration-style
- text-emphasis
- text-emphasis-color
- text-emphasis-style
- text-indent
- text-orientation
- text-overflow
- text-transform
- text-underline-position
- unicode-bidi
- vertical-align
- voice-family
- width
- word-spacing
- writing
Supported media queries
- all
- screen
Supported queries
- min-width
- max-width
- min-device-width
- max-device-width
- orientation
- min-resolution
- max-resolution
Supported keywords
- and
- only
More source information can be found under https://developers.google.com/gmail/design/css
