Well we need more information first. Are you checking it using POP3 access through the Blackberry program, are you using a stand-alone applet (something like the GMail applet used for GMail), or the website--and if the latter, which browser.
Also which Blackberry is it, and are you using BIS, BES or some other setup? Who's the phone carrier?
Posted from my CrackBerry at wapforums.crackberry.com