AVIF, or AV1 Image format, is the latest image compression format available. AVIF is a format for optimizing images to make them smaller while maintaining the same quality (lossless). AVIF files have an extension of .avif. AOM developed AVIF to provide royalty-free images with better compression efficiency and more features than the existing formats. AVIF is compatible with high dynamic range images, just like its predecessors (WebP, JPEG-XR, JPEG2000, and PNG, GIF). The format supports 10- and 12-bit color at full resolution, producing images up to ten times smaller than other formats. The AVIF format is a game-changer that will soon become the default image format in the world. As a result of its potential features, likely, it will quickly be supported across all platforms.
A mail client included with Apple Inc.'s operating systems macOS, iOS, and watchOS is Apple Mail (officially known as simply Mail). As part of Apple's 1997 acquisition of NeXT, Apple Mail arose from NeXTMail, which NeXT initially developed as part of its NeXTSTEP operating system. Apple Mail uses SMTP for sending messages, POP3, Exchange, and IMAP for storing messages, and S/MIME for encrypting messages end-to-end. Furthermore, it has been pre-configured to work with popular email providers, including Yahoo! Mail, AOL Mail, Gmail, Outlook, iCloud (formerly MobileMe), and Exchange. iOS includes a mobile version of Apple Mail, which supports the Exchange ActiveSync protocol (EAS). However, until the release of iOS 9, Apple Mail did not support attaching files to replies. In Apple's Mail app for macOS, EAS is not supported. The main problem is that sent messages will be incorrectly duplicated in the Sent Messages folder, propagating via syncing to other devices, including iOS. It is possible to configure Apple Mail to receive all users' email accounts in one list, organize emails into folders, search for emails, and automatically append signatures to outgoing emails. Additionally, it integrates with the Contacts list, Calendar, Maps, and other applications.
To this date, Apple Mail does not support AVIF images. You can attach AVIF files as you would attach any other files, but you won't be able to attach or view them inline.