If you or your students have limited bandwidth or access to technology at home, you may want to use institutional email for most course communications with optional materials to be sent to the students via email attachment, or even US mail. However, to protect students (FERPA) while teaching remotely, you will need to use the Course Gradebook in your institution's LMS, or call students to communicate grades. Please see the Keeping it Simple : Low Bandwidth/Access Teaching Strategies for helpful considerations for teaching remotely.