To my best knowledge (which isn't good by the way ;) delayed emails are usually the cause of a RIM problem or possibly with your service provider. It happens to everyone from time to time. Like the other day it was about an hour or so before I got any emails and I knew I had emails waiting. But if it happens everytime, then you need to call Cingular and then if they can't help, they should transfer you to RIM. You'll be on hold a while so call from a land line and settle yourself in front of the TV or something...
'I am stuck on Blackberry and my Blackberry's stuck on me'