BeeFree.io - Bee is MailUp's drag-&-drop editor for responsive design emails.
OpenToonz - OpenToonz is an animation program that is a free software version of Toonz, the animation software...
Topol.io - Create professional Email templates easily - Drag & Drop Email Builder.
Synfig Studio - Just another WordPress site
MJML - The open source framework for responsive emails
Adobe Animate - Adobe Animate is a Flash, vector animation software.