Can I create an email group to send email to all my class mates?
If you wish, you can create a globally available group alias for all your class mates. That way you and your class mates can email to a single address, and all will receive the emails.
You can manage this via Lifetime Email's "Google Groups", accessible at http://groups.global.t-bird.edu
There are numerous options when you create groups, including who is a member, and who can send to the group. Please see the Google Groups help pages for more.