This was a great app and worked fine for years, until Microsoft either started proxying requests or their proxy started not working correctly. In my Exchange logs all of the ActiveSync traffic comes from MS-owned IPs rather than my phone's external IP. Emails are delayed from showing up in my mobile Outlook inbox until minutes-to-hours after being delivered to Exchange and my desktop Outlook instance. I tested this on multiple phones and even another Exchange server, and in all cases the behavior is the same. It's completely unnecessary to proxy this traffic, and just leads to unfathomable delays. I switched my account over to the GMail app (also using Exchange/ActiveSync) and it works fine because that app communicates directly with my Exchange servers.