@analyticalminds ...

I do not think this is possible, unfortunately.  There is no "admin" functionality in Free For Teachers (FFT) version of Canvas, so you wouldn't be able to do this.  Further, I'm not sure this is even possible in the paid version of Canvas.  I know that you can change the name of who it comes from at an account level (for example, if you wanted it coming from your school's name instead of Instructure, you can change that name), but it still comes from notifications@instructure.com.