I have a single POP3 account on the stock email app and I have it set to automatically send/receive every hour. Sometimes it does indeed check on one hour intervals, but often I notice it's been several hours since the last email check, so I have to do a manual refresh. I'm wondering if somehow my data is getting turned off when the screen is off, and this causes the problem. I notice that sometimes when I turn my screen back on there's no '3G' displayed at the top, but after a few seconds the 3G appears. But I'm noticing the same problems when connected to wifi too. Would having "Enable always-on mobile data" unchecked cause this issue?