You can with 1Tool also edit existing newsletter templates.
Go to it Administration – Marketing – Newsletter – Newsletter templates.
Now click either on the button “Create new template“ to create a completely new template 
or change an existing template using the WYSIWYG editor 
.
WYSIWYG editor
If you have no knowledge of CSS or HTML, we recommend editing using the WYSIWYG editor. This enables a so-called real image display and therefore shows your template on the screen exactly as it will be displayed later.
The editor will now open and you can start with the basic settings for the template (on the left under “Template Settings”). These settings, such as font colors, buttons, etc., are also always visible on the right in the template itself and are therefore displayed exactly as they will appear when the newsletter is later sent.
HTML Editor
CSS editor
Start your settings under the tab “template".
Under the tab “font” you can make all the settings for your individual headings and the text area.
Finally, you have the option under the section “Button” to design your buttons. Here you can specify the color, rounding, etc.
About the tab with the question mark icon The most important placeholders for your newsletter template are displayed to help you. For example, this could be an unsubscribe link for your recipients or the online view of your newsletter.
Your template is visible to the right of your settings. Your settings/changes to your fonts, buttons, spacing, etc. are displayed here in the content area. Above and below you can see a blue "plus" symbol. You can use these buttons to Header and footer for your template so that you only have to enter recurring or constant information, such as your contact details or your logo, once. You can then create your final newsletter based on your template, whereby you only have to insert the newsletter text including images, buttons, etc., since the header and footer are now automatically set up for each newsletter as you define it in the template .
The insertion of content such as texts, images, buttons etc. is possible under the menu item “Insert newsletter content” explained. The insertion of content is always carried out in the same way, both in the newsletter template and in the final newsletter creation.