iPhone mail not automatically checking for mail
I just got my iPhone 4 yesterday and I'm a pretty tech savvy teenager. However, my mail isn't automatically checking for new mail. I want it to alert me whenver I get a new email, but it will only check for new mail when I physically open the mail app. I've searched everywhere in the settings and can't find anything to change that would automatically check for new mail. Maybe I'm just overlooking something? Could someone please help me figure this out?
Thanks!
iPhone 4