You cannot undo the changes if you mark all messages as read


Symptoms


If you have many read and unread items in a message folder in Microsoft Outlook, and if you inadvertently select all messages in a folder to be marked as read, there is not an option available that allows you to undo this selection.

Cause


This behavior is by design.

Once you have set the folder and all items in it to be marked or flagged as read, you must manually re-set the message items back to their prior status.

Workaround


You can select all of the message items and mark them as read or unread. However, this process is different than returning them to the read or unread status on an individual basis as they were before you marked them all as read.

To work around this behavior, manually re-set the message items back to their original status. To do this, use the following methods.

How to mark all folder items as read

  1. On the View menu, click Folder List.
  2. Right-click the Folder, and then click Mark All as Read.
All of the message items in the selected folder are marked as read.

How to mark individual items as unread

Right-click an item in a folder, and then click Mark as Unread. This returns the individual message item to the unread status.