I was recently in Outlook in my Inbox, and did a search (default: Current Mailbox). Most results were things I'd sent, and so were marked unread. A bit later, I returned to the search results, but thought I was looking at Sent. I clicked "Mark All As Read" which I periodically do on sent mail as there is no "Mark as Read" action available to rules being applied to sent messages.

However, this had the effect of marking all the messages in my Inbox as read, including several I had marked unread because I needed to return to them.

How do I undo this?

The computer synced quickly with the server after the erroneous Mark All As Read, so interrupting prior to that happening was not practical. Folders other than the Inbox were not affected.


If you have another machine that regularly syncs to the same inbox, get that machine offline before opening Outlook. Then, open Outlook and do a quick search for unread messages in the Inbox folder. Mark those with a specific color Category (that you don't otherwise use) and then go back online and sync.

Then, sync with the new machine, search the Inbox for messages in that category, mark those as unread, and remove the category designation. Re-sync and you'll be good.

However, if you don't have another machine which recently synced to the server, you'll be out of luck. You'll also lose recent changes in what was marked read/unread, including the applicability to recent messages.


Theoretically, this is by design that there is no option available in Outlook that allows you to undo the "mark all as read" action. See the official link below for more information:

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

To make things easier, you may refer to the link below to sort emails by icon before clicking Mark as unread:


  • Bad design decision on Microsoft's part. Thanks for posting the official link (which includes a feedback form at the bottom of the page)! – WBT Aug 13 '18 at 17:31

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.