Creating a class email list can be a simple way to keep your students up-to-date with announcements on course events. Instructors can use SPIRE to create, refresh, and delete class email lists. This will generate a single email address that lets you email all the students enrolled in the course at once.
More information at:
http://www.oit.umass.edu/spire/for_instructors/class_information/mailing_list.html
Tip: Your enrollment will be in flux during add/drop so it is best to not rely heavily on email lists until after your roster has settled down (usually 2 weeks into the semester).