Hello and good afternoon. I'm sorry to hear you're having issues with Outlook mobile and EAS. Please be aware that Outlook Mobile leverages EAS 14.1, and so may experience misc issues due to it not leveraging the latest EAS schema version we have included in SmarterMail (v16.). Do you have these same results when testing under the OEM email and calendar applications that are included with the device? 

The client says they are also seeing this issue when entering calendar meetings in Outlook Desktop.

Version: Microsoft Outlook 2019 MSO (Version 2109 Build 16.0.14430.20154) 32 bit

I don't know about the OEM