Symptoms
Assume that a user creates a message draft by using Outlook in online mode in Microsoft Exchange Server 2016 and leaves the draft open for a long time (for example, multiple minutes). When the user finally sends the message, he receives the following error message:
The function cannot be performed because the message has been changed.
Cause
A conflict exists because of the auto-save feature in Outlook. A save event triggers the agent on the server that's modifying the message while the Outlook client still has the message open. To reduce the conflict, the FORCE_SAVE flag is added for items that’re saved in the Drafts folder in Outlook to make sure that the items can be successfully sent in this scenario.
Resolution
To fix this issue, install the Cumulative Update 15 for Exchange Server 2016 or a later cumulative update for Exchange Server 2016.
References
Learn about the terminology that Microsoft uses to describe software updates.
