Xmind - Xmind is a brainstorming and mind mapping application.
Stripo - Stripo is an all-in-one email design platform. We enable our clients to build emails of any complexity, including interactive AMP emails, really fast and easy.
MindMeister - Create, share and collaboratively work on mind maps with MindMeister, the leading online mind mapping software. Includes apps for iPhone, iPad and Android.
MJML - The open source framework for responsive emails
Viima - Viima is the simple, yet incredibly powerful Agile Innovation Platform that helps you go from ideas to innovations – at the speed and scale of a true innovator.
Templates by Email Monster - Hundreds of free, responsive email templates. Pick and edit.