Shanon,
If you're using Alfresco, task-completion emails are built in (by checking the "notify by mail". This is the same email, for all types of tasks and can be configured as a .ftl-template in the repository. If you want to have custom emails for each type of task (or on assignment), you'll have to plug in another task-listener (as the TaskCompleteListener is, e.g..) for all user-tasks, using the BPMNParselistener that already exists in alfresco, or an new one… The task-listener can also be added explicit ally in the BPMN20.xml-file, not requiring a parse-listener solution…