Cause
The Send Email tool was removed from the "My Institution" tab.
Resolution
There is no known resolution at this time.
Workaround
Instructors
You can still access it from within your course. To do that, expand the Course Tools area in the Control Panel on the left menu. It will work exactly as it did from the "My Institution" tab.
Students
If you have questions regarding the send email feature, you will need to speak with your instructor to see if they have linked the tool in the course.