HTMLメール CSSガイド14 November 2017 Outlook.com and the Outlook iOS app added support for CSS background images and some related properties, as well as certain Flexbox and Grid properties. Also added iOS 11 Mail to the guide, with no noticeable differences from iOS 10. 22 September 2017 Microsoft updated the Outlook apps for iOS and Android with more consistent CSS support, including media queries. 13 September 2017
