As the Project Admin you can set the default auto-text (template) for a specific mail type.
The project auto-text template you create is specific to your project and your organization.
If Mail and Document types for your project are locked, you won't be able to set default auto-text for mail types.
Even if your project's Mail and Document types aren't locked, the default auto-text template you create can be overridden at:
If the Edit button isn't available, the Mail and Document types for your project are locked. To unlock these you'll need to disable the following project preferences:
Once these preferences are unticked and saved you need to refresh the page and the Edit button will be available.