While we typically recommend using HD video to display cinemagraphs on the web, email is an exception. GIFs are the only reliable file format because you can't control autoplaying and looping video within emails. A GIF is the only file type that'll autoplay and loop your cinemagraphs for most email clients.
There are a few ways you can save your cinemagraph in GIF format. The easiest way is by exporting your cinemagraph as a GIF from Cinemagraph Pro for macOS. Select Export (⌘E) at the upper right side of the app or under the File menu. Select Animated GIF under Format.
A cinemagraph loop of 1 - 3 seconds is ideal to keep the file size down. If you’re sending emails to large companies, they may block messages that are unusually large. Try and keep the total size of your email, including the GIF and any other content, down to 10MB or less. The example below is only 300 x 300 and 695 KB which would work perfectly for emails.
Cinemagraphs by Andrew Pavlidis, Cflow, and Apricot Berlin
Read Saving Cinemagraphs in GIF Format to learn other ways you can save your cinemagraphs in GIF format.