It is possible to modify the display of unread and total messages for different Mail folders. This feature is useful for the “Inbox” folder. However, if you wish to determine the total number of messages (both read and unread) in other folders like “Deleted Items” or custom folders, what can you do?
Access the Outlook 365 webmail settings by clicking on the gear icon located at the top right corner of the screen. From there, select “View all Outlook settings” at the bottom of the dropdown menu. Navigate to the “Storage” option under the “General” tab to view the size and number of messages in each email folder.
I haven’t been able to locate a feature that displays the overall number of Contacts and Calendar entries.
The feature is not currently accessible on OWA, but it has received a high number of votes on uservoice.
Outlook on the web (Office 365)
Another option is to access the folder’s right-click menu and choose
Mark all as read
. This will trigger a confirmation prompt similar to the one shown below, which will display the number count.
If the option appears disabled, you may choose to employ the shortcut CTRL+A (or ⌘+A on macOS) to choose all contents of the folder, and then proceed to attempt
Mark all as read/unread