Assume that you are using Microsoft Outlook in online mode in Microsoft Exchange Server 2019 or Exchange Server 2016, and you perform one of the following actions:
You try to move a folder to a target folder that contains a folder that has the same name.
You try to delete a folder so that the folder is moved to the Deleted Items folder. However, the Deleted Items folder contains a folder that has the same name as folder that you want to delete.
In this situation, the operation fails. The moved or deleted folder still exists in the original location. However, Outlook does not display an error message to indicate the failure.
If you try to move the folder by using the Outlook on the web (formerly known as Outlook Web App), you receive the following error message:
The folder couldn't be moved or copied. A folder with the same name might already exist.
If you try to delete the folder by using the Outlook on the web, you receive the following error message:
The folder couldn't be deleted. This may have occurred because a folder with the same name already exists in the Deleted Items folder.
This issue occurs because the Exchange Server 2019 or Exchange Server 2016 does not return the appropriate error code to Outlook. Therefore, Outlook does not detect the operation failure.
To fix this issue, install one of the following updates:
Learn about the terminology that Microsoft uses to describe software updates.