My push notifications for my e-mails aren't working. At first, I would never get a notification sound or an alert of any kind and would just see a bubble over my email icon with a number in it. Now, it doesn't even do that. I even e-mailed myself and I have an e-mail in my inbox and the phone isn't alerting me or showing a bubble on the e-mail icon. I'm not having this problem on the Gmail app, just the stock e-mail app for Yahoo and AIM/AOL. How can I fix this problem?