Assuming that you and your students are trained to use email, your basic consideration is how to process the email you receive.  Here are some guidelines:

• Make a mailbox for each class you are teaching in a given semester with a name different from the names of all earlier mailboxes.
• Even if you learn how to use filters, do not use filters to pre-screen your email into the various mailboxes.  Leave them "in your face" in your In box so that you'll deal with them before transferring the message and your answer into the appropriate mailbox.
• Delete an email only if you are sure that you'll never have to deal with it again, didn't want it in the first place (wrong recipient or junk mail), won't want any information from it including web site URLs.
• In your address book, make a tag for your class and list each student's  email address with it so that you can send email to each class member at one click of your "Send" button.
• Use some early emails as tests to find out what kinds of attachments class members can send and receive, e.g. Word7 documents (everybody who has Windows 95 has WordPad, a trimmed version of Word6), Excel spreadsheets, .gif or .jpg pictures, or other files that you might or they might use during the course and post results to the class. 
• Consider forming email groups for one of the following purposes:
  • a classroom committee 
  • group study of one course concept: Count the emails as a quiz check or grade or as extra-credit.  In your directions, have students include your email address in the cc: line of their email to group members.  Keep received messages in the class mailbox or make a container for each group inside the class mailbox.
• Consider listservs for yourself and/or your students.