Today I ran into a frustrating issue with Outlook 2013 where a user received an error saying “The operation cannot be performed because the message has changed.” or at times “The operation failed. The messaging interfaces have returned an unknown error. If the problem persists, restart Outlook”. The errors would come up when she tried to send a message AFTER when Outlook was set to save a draft (in this case, 3 minutes). When this happened, she couldn’t send the message and would have to copy and paste the contents into a new composed mail in order to send it. This was in a terminal server environment and she was using an Exchange account that’s hosted on Office 365. While researching the issue online, I saw that users using POP3 and IMAP accounts were experiencing the same thing without a long-term resolution. The short-term resolution was to disable drafts completely but that was not acceptable here.
I tried recreating her Outlook profile, ran Outlook in safe mode (no addons), and extended the autosave for drafts from 3 minutes to no avail. Finally, I discovered the magic solution.
Disable “When a reply modifies a message, don’t move the original.”
Go to Options > Mail > Conversation Clean Up > and uncheck “When a reply modifies a message, don’t move the original.”