Scenario:
We added a Feedback to the front page of a site, and emails were not being sent.
Solution:
We added an individual as a Teacher (not an Administrator) using the 'Locally assigned roles' of the Feedback activity.
Emails sent - no problem
This is a specific solution when using the Feedback module on the front page of a Moodle site. Adding the Feedback activity to a Course may well send the email to the Course Teacher(s) anyway?
Hope this help, Stuart.