Outlook 2019 issue

[BO Terry]

*Edited* I have a client using Outlook 2019 for his email. His mail provider is 1and1 Ionos and the email is set up in Outlook as IMAP. He received the following error message last fall and it came back again last week.
The error messages is:

"The operation cannot be performed because the message has been changed."​

In the fall, here is what fixed it.
"Open Outlook > File > Options > Mail > Under Conversation Clean up, Uncheck When a reply modifies a message, don't move the original > Restart Outlook (it is is already unchecked, check it Restart Outlook, Uncheck it and Restart Outlook)"

When I went in last Friday, the settings were still as I had changed them to last fall so I did the check Conversation Cleanup > restart Outlook > uncheck Conversation Cleanup again > restart Outlook again. Today, it happened to him again so I'm still looking for the solution.

Another suggestion with the "fix" mentioned above is shown below but I'm not comfortable with it.

"Account Settings > Open your account > More settings > Under Advanced tab, put INBOX in Root Folder Path. (If your all folders disappear, simply remove INBOX from here)"

Any other suggestions to address this?

*Update 3/18/21: I heard from my client this afternoon. He is still having this issue and it's getting progressively worse. Now, it's happening with new emails as well as existing threads that he is responding to. I tried testing putting Inbox in the Root Path Folder of my own computer (I use webmail but have Outlook too). When I added Inbox to the Root Path, I only had the main Inbox, none of the folders that I see in Webmail as well as what I see in Outlook without this adjustment. The folders did return when I removed it as stated in the steps above but it didn't leave a warm fuzzy feeling for this fix.

I began wondering today about two more options.
1: I'm willing to bet that he rarely closes Outlook unless there is an issue. I thought I may suggest that he close it at least once daily to help with the issue (clearly not a fix).

2: I wondered if creating a new profile may help.

 

[HCHTech]

You didn't lead with the problem, so I'm not sure I'm understanding correctly, but it appears this is related to the 'conversation view' setting. So, what happens if you turn off conversation view?

 

[BO Terry]

You didn't lead with the problem, so I'm not sure I'm understanding correctly, but it appears this is related to the 'conversation view' setting. So, what happens if you turn off conversation view

I edited the post. Turning off conversation view helped for a while but the issue came back.

 

[HCHTech]

Long thread here on this issue. Give it a read through and see if one of the suggestions helps.

 

[BO Terry]

Long thread here on this issue. Give it a read through and see if one of the suggestions helps.

Thanks @HCHTech. This thread is actually where I found the first fix and I will continue through it for other options. There is another solution that looked promising further down in "Vijay" suggestions but someone who tried it lost some messages.
(Account Settings > Open your account > More settings > Under Advanced tab, put INBOX in Root Folder Path. (If your all folders disappear, simply remove INBOX from here).


I'm pretty sure I tried online repair last fall but will try that again when I connect with them again.

 

[HCHTech]

I noticed in one of the searches I did that someone called it a bug in the latest release, although I don't think that was a MS comment, so it's probably just run-of-the-mill IMAP sync problems. That thread I referenced points to a problem with the message getting copied to the Drafts folder while you were editing it for a reply, and their fix being to copy the contents of that email out of Outlook temporarily, then deleting the message and anything in drafts, followed by creating a new message, pasting the content back into it and sending that...

 

[fincoder]

I get that sometimes after opening an attachment, closing it, then trying to move or delete the message. It's annoying, but easily resolved by closing Outlook and opening it again, then the email moves or deletes normally.

 

[BO Terry]

I get that sometimes after opening an attachment, closing it, then trying to move or delete the message. It's annoying, but easily resolved by closing Outlook and opening it again, then the email moves or deletes normally.

I too have seen that this works but it's not a good answer for my client. Frustrating that it's still an unresolved Microsoft issue. Or, would that be considered what we used to call an "undocumented feature".