Outlook Notifications from Entity Activities Issues

I have integrated Dynamics CRM with Outlook using the outlook app and connecting it via the Email Settings in Dynamics. 

I have added a few users and they are reporting that they are not getting outlook alerts for Dynamics Activity due dates (phone calls, tasks, etc). The users that are getting notifications, are getting them about 4 hours late. This brings me to two questions:

- How can I enable users to receive Outlook notifications on activities that they set in Dynamics?

- How can I make it so the alerts feed to Outlook before the activity due date rather than 4 hours afterwards? We are in central standard time. It almost seems like our Dynamics is using another default timezone.

Thanks!