GIFs are supported in our editor. They work the same as uploading a normal image to the media library and inserting it into your content.
We recommend the file size not exceed 50 KB. The email will send fine if the GIF exceeds that file size however it will take a while to load for the contact.
Outlook does not support the animation of GIFs. In Outlook, the GIF will display the first frame as a static image.