Send reminder to students who are yet to submit assignments

You can use the Gradebook to send reminder messages to your students:

Go to Grades from your Course Navigation,
For the assignment/quiz item that you want to send a reminder, click the Options icon.
Click the Message Students Who link. In the For students who... drop-down menu, select the category, "Have not yet submitted" students you want to message.
You can manage individual recipients included in a message by clicking Show all recipients. To remove or add students, click the Remove (x) icon or Add (+) icon.
The assignment name is usually auto populated in the Subject field.
Key in your message to the students in the message field and click Send. Each student will receive an individual message, although you only create one message to be sent to multiple students at the same time.

Message to students can be filtered based on the following options in the For students who... drop-down menu:

Have not yet submitted: students who haven't submitted the assignment.
Have not been graded: students whose assignments have not yet been graded (submitted or unsubmitted).
Scored more than [point value]: students who earned a grade on their assignment more than X number of points.
Scored less than [point value]: students who earned a grade on their assignment less than X number of points.