If you are working on a task:
When you complete a Task that is part of a PBI you need to send a done email to the Owner of that Story.
You only need to add the Task #, Summary and link to the item in WIWA. Remember that all your tasks should be under 4 hours, do spending lots of time on a Done Email for a Task would be counter productive. Add more information if required, for example you may have completed the task a different way than previously discussed.
Make sure that every PBI has an Owner as per the rules.
If you are the owner of a PBI:
When the last task/bug of a PBI is complete, you then send a comprehensive done email as per the rules when the story had been completed. Make sure you add a list of all of the Tasks that were completed as part of the story and the Done criteria that you completed.
Here is the Done Criteria we followed:
a. Compiled/Built locally
b. >30% Code Coverage
c. All unit tests passed
Then add an illustration to show this.
Figure: Good example - This is proof you have met your 'Done criteria'.
This is all designed to help you Scrum Team members (Product Owner, Scrum Master and Team) keep a certain quality bar on completion of each chunk of work. Remember that you are not 'DONE' until your team says you are done.