is it possible to modify email template (*.ftl) or to create a new one ? simply modifify a template like notify-user.ftl seems not work. How can i do to have a new template.
You can modify the template by simply editing the .ftl file in the Email Templates folder in the repository. You can make new email templates by simply adding new .ftl files in the same location. See these docs for more info on writing working template files: http://wiki.alfresco.com/wiki/Template_Guide