Using Classic Outlook on Windows for personal email, calendar, and contact management
Hi All,
First, apologize for the inconvenience caused by this problem in Outlook Client. Microsoft has realized this issue and the dedicated outlook teams are working on this problem to fix it. It is a known issue in the current Outlook Clients, and a fix will be released to Office version 2106 on 2021/6/17. For the affected users please navigate to Outlook Web App as temporary workaround and wait for the new fix release with some more patience, thanks. For more details, please refer to "The properties of the message have been changed" prompt when forwarding/replying in Outlook.
Thanks for your understanding and patience.
Best Regards,
Oliver