Yes, you can add a default message, name and subject line to your team account(s). In the prepare view you can still manually override the message if needed.
1. Log into the specific team account.
2. In the menu (upper right corner) select 'Teams'.
3. Click on the 'Advanced' button.
4. Add the your subject line, message and optionally a landing page.
5. Click 'Save'.
Optionally, if the document is the same, you can create a template of your document and add a specific subject line and message to your template(s).