Before email learners had to ask a question in class or ask a question of the instructor before or after class. Many instructors see this as an increase in workload. But before the advent of email those question may never have asked or answered. It is a great advance as far as learning is concerned. Instructors with large classes should seek help from graduate assistants or perhaps use other methods of managing their email.
Faculty can setup filters to funnel email based upon course or subject matter.
Filtering strategies should be developed with the student's need in mind. They may be added work but let's not forget that they are they whole reason for course delivery. Email also can be used to promote discussion. Depending upon subject matter, group discussions can facilitate learning. In addition course listservs can be set-up as a way to broadcast information to the group.