Actually, it’s crucial that you read your email every day. If your professors ask you via e-mail to prepare something for class, you’ll be expected to know that information. Also, don’t underestimate the power of a well-written e-mail to your professor. Often, an e-mail exchange is the easiest way to really understand a difficult point.
Saying that you "didn't check your email" is not a viable excuse for missing pertinent information given to you from your professor. It is your personal responsibility to always check your email, maybe 3-4 times per day. You never know when you might receive a crucical email.
Rule of thumb: check your email as much as you check your Facebook and you'll be okay.