You can use the Unread Search folder in Outlook desktop software to find unread messages. However if you have more than one account or data file in Outlook, you'll need a search folder for each data file.
Or you can use Instant Search with the search query:
Tip: Isread: no will work in both Outlook desktop and Outlook on the web.
Using the Instant Search method, type read:no in the search field and select Current Mailbox or All Mailboxes from the menu or Search ribbon button.
The Current Mailbox search will include unread messages from all folders in the current data file, while All Mailboxes will search all data files in your profile.
Depending on your version of Outlook, the results are limited to 250 messages in the initial results, which is fine if you are good at marking your email read, otherwise you need to click again to view all unread messages.
With an Unread Search folder, your search is limited to one data file per search folder, so you need one search folder for each account. You can use a search folder to search all folders within the data store or restrict it to the specific folders, such as your Inbox and subfolders.
You can add the search folders to the Favorites list so they are convenient to access. If you view the search folders regularly, they should update as new mail arrives. Search Folders can be set as the Start-up folder; this is the folder Outlook shows you when you first open it. The startup folder is set in Options. See Choose the Folder Outlook Starts Up In if you need the exact steps.
If the Unread Search folder is not on your Favorites list, look for it under Search Folders. You can drag it to the Favorites pane or right click and add it to Favorites. If the Unread folder is not listed under Search Folders, right click on the Search Folder then create a new search folder. For help creating search folders, visit our search folder tutorial
Robert Aldridge explains how he uses an Unread Search folder:
Normally my Outlook is set to Conversation view. That makes it a little difficult to catch-up when I’ve been out of the office, because the “unread” messages are combined with the “read” messages in the Conversation view.
So my Search Folder is called Unread Inbox and combines all of the “new” items into one view. Then I can quickly scan for important messages, and optionally, use Control-A to mark all messages and then use “Mark as Read.”
In Outlook 2000 and later, after you receive new mail, the Folder List opens to show any folders in the hierarchy that have new, unread items. Other than that, Outlook does not provide much help in locating unread items.
One method would be to use Advanced Find to search all your folders. HINT: The More Choices tab has an option for finding unread messages. If you use Advanced Find in this manner often, you might want to use File | Save Search to store your search criteria for easy reuse. Note that Save Search is disabled or removed from newer versions of Outlook due to security concerns.
Otherwise, a few third-party tools provide some assistance in locating unread items.
NEO FIND organizes all emails automatically in the most logical and intuitive way people think about their messages: around the correspondent involved in the email communication. Adopting Caelo's patented virtual folder structure all emails (both sent and received) are organized in a Correspondent folder. This folder can be searched or filtered to quickly zoom-in on the message needed.
NEO Pro is an email organizer and search engine for Outlook that indexes emails (including multiple message stores), as they are sent and received, into convenient virtual folders such as Correspondent, Date, Attachment Type and Category for instant access. NEO Pro introduces Conversation View, which allows users to expand the thread in the message list. Includes email notation so that users can add notes to individual messages for future reference.