Templates
Designed, not default.
A hundred starters that vary in colour and design — quiet and monochrome, or bold and colourful. Filter by category and colour. Every one renders the same in Outlook 2016 and on a phone in a truck, and will still look fine in three years.
Bring your own HTML if you have it.
Drag-and-drop or a Monaco editor with live MJML preview. Both validate the unsubscribe tag on save.