So I've been searching around and not finding an answer. I have US Cellular and have the Motorola Electrify, which is the same as the Photon. My email won't sync as the email comes in. I have to manually refresh it. I don't know what is going on. It worked and now it doesn't. My Facebook and Twitter apps are coming in like normal so the background data is running. I can't figure it out otherwise.
Are you using Gmail? Check the android market for an update. Search for the app and see if it says update or installed. You should be able to hit the menu key while in the email app and select how often you want the app to check for emails. I use Gmail for my Facebook and yahoo for everything else.