There are 3 editors available to create email template

1. Drag & Drop Editor
2. CKeditor
3. HTML Editor

How to create email template

1. Go to Extensions > Extensions > Productivity Apps > Email Template Designer
2. Click on Create Template button at the right top. A popup will appear.
3. Enter Label to the template and click on ADD. The template will be created. Close the Popup.
4. Click on the edit button for the newly created template.
5. You will find 3 modes to edit the template. Choose the one as per your requirement

Once you choose a mode for an email template, you cannot change the mode.