Galaxy S6 :: Why Stock Email App Not Syncing And Not Accepting Automatic Push Notifications

I am using Microsoft Exchange with Active Sync through my email provider, Intermedia. The sync has been erratic at best. I have put all of the email settings to Auto; however, most of the time it only syncs when I push the email icon. I've tried calling Samsung and AT&T - even had a remote session with AT&T. They could find nothing set up improperly. I've deleted and re-installed the email app a few times. I got it to work over the weekend, but yesterday, it stopped syncing again. I would even delete specific emails from the phone and a few minutes later, they would show up as unread.

I've called my email provider and went through troubleshooting with them, to no avail. Everything was setup properly. I've wiped the system cache a few times. I just tried the following: deleted the exchange email setup from the phone (again for the 3rd time); went into application manager and cleared the data from every "email" app that was in there (email - there were two, email synch, email storage, etc). Then I shut down the phone and did another wipe of the system cache. Then I installed the email app again.

Now it seems to be working. I'm just afraid that, after a period of time, it will stop working. My 14 day period ends on Thursday. I'm thinking about exchanging this phone for another S6. However, what if it happens on that phone. I've asked AT&T and Samsung if they have any information in their database regarding this issue and they both said no. I even tried to use the Microsoft Outlook app. But it doesn't appear to be able to work with Active Sync (I can't put my email server parameters in there).