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.
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.