By creating a MySanDiego account, you also create your email account.  This username gives you an e-mail address in the format username@sandiego.edu and also gives you access to a number of other services.  With a MySanDiego account, you can check grades, register for classes, use Blackboard LMS, publish a web page, forward e-mail, create a vacation auto-reply, change your account password and download anti-virus software.