Many users report the error message “The operation cannot be performed because the message has been changed” on Outlook while connecting to Microsoft Office 365 Office 2021, Office 2019, When we receive an error message while sending or opening an email in Microsoft Outlook on web, see the cause and understand how to fix it.
read more here
https://www.officelivesupport.....com/fix-error-messag

 

www.officelivesupport.com

Operation Cannot Be Performed the Message Has Been Changed

Operation Cannot Be Performed the Message Has Been Changed error occurs when attempting to perform an operation on a message or data object..