I was testing my phone and found that if i JUST set it to sleep it will notify me of new emails. But i waited until it was asleep for over 25 min and i sent 2 emails from 2 different email accounts and neither one showed up on my phone until i unlocked it and hit airplane mode and then unchecked airplane mode. i have the mobile data set to always on. I do have only 1 bar at -99 signal strength. but if i turn on and off airplane mode the emails come right in after a prolonged sleep. i'm going to see if i can reproduce this issue.