Hello, I've gone quite far with this and have even talked to the expert on Outlook for iOS here at Microsoft Ignite. Here is what I've done so far:
Opened up tickets with Apple, Microsoft, and VMWare.
Both Microsoft and VMWare are stating that it's purely an Apple issue as ActiveSync is responding back properly but the client is not, confirmed with logs using Wireshark and decrypting the traffic.
Apple Enterprise Support responded with the following:
' Thanks for reaching out to AppleCare Enterprise Support Engineering for assistance. I understand you're experiencing several performance difficulties with iOS 13 devices interacting with your Exchange infrastructure. I have received the following list of issue symptoms relevant to your environment:
1. When forwarding and replying to emails, it is truncating the email
2. When emails are marked read or reply to emails, the message isn't successfully marked as read
3. Intermittently the Mail app will not actually download new messages that are on the Exchange server, but show that everything is up to date.
At this point, I can confirm that Apple is tracking behaviors related to each of these issues, and is working to address each in a future update (or updates). I can't provide ETAs on patch releases or similar, as long standing Apple policy prevents discussion of unreleased software.'
I've confirmed with multiple people at Microsoft (including here at Ignite) that Outlook for iOS will not work due to changes in architecture. I'm still diving into it but it looks like we'll have to use MAM with Intune and possibly create a separate ActiveSync URL that's locked down to the EXO IP address range. The Microsoft expert who wrote the following article told me to read over it: https://docs.microsoft.com/en-us/Exchange/clients/outlook-for-ios-and-android/use-hybrid-modern-auth...
I do still have some questions regarding the article like the ActiveSync URL configuration if we were try and run it in parallel as he suggested, and if we can enable HMA with 2010 servers if our live mailboxes are all on our 2016 CU 14 servers.
I guess at this point, it's up to Apple to fix or we start looking at other clients, or possibly replacing AirWatch with Intune which Microsoft is pushing.
