It is possible to customize the notification e-mails by modifying templates. For example, the "plain.tpl" template located in the "templates/notification/handler/ezgeneraldigest/view/" directory of the standard design is the main notification template. It controls how the e-mails will be generated.

If you need to make changes to this template, you should copy it to your custom design and change it there. For example, you could copy it and add some additional/static text that will appear in all e-mails that are sent out. Remember to clear the caches before testing the changes. Please note that you should not change the default template but instead copy them to your own design.