I have the same problem. It's incredibly frustrating. So far, I've reinstalled my email accounts from scratch three times! The last time, based on something I read online, prior to re-installation I turned off the iPhone's WiFi and reset the network settings. I thought I had it licked, because it properly retrieved email for almost a day -- a record since I bought the iPhone a month ago. Like many people, sometimes re-setting the device fixes the problem, sometimes not. But needing to do that two, three times a day is clearly not a solution. Especially when it doesn't always fix the problem. I have to say, my love and loyalty for Apple is being strained greatly by this whole experience. I can accept getting a one-off defective product -- sometimes that happens in the manufacturing process and any good company will replace that product. But it seems in this case, Apple (knowingly?) released a fairly pricey device way before it was ready for prime time. Thousands, maybe tens of thousands of people are having the same difficulties. I hope Apple solves this issue soon. I'm actually becoming jealous of my friends who have properly functioning Blackberries!