Messages in the Sync folders are only visible within the Outlook client on your machine, so you won’t find them in the Outlook web app.
This changes the view in the Navigation pane to show all of the mail folders in your mailbox, including the Sync Issues folder and its three sub-folders. At the bottom of the navigation pane click on the ellipsis (the three dots) and select the “Folders” option. You won’t see these folders by default in the navigation pane in Outlook, so we’ll start by making them visible.
Scroll down towards the bottom of the list to find the Sync Issues folders. Its View Mailbox Size feature shows you the size of all of the folders in Outlook. If you’ve never used it before, check out our guide to using the Mailbox Cleanup tool.
