Outlook is not showing all IMAP folders
You may find differences between your webmail folder structure and the one displayed in Microsoft Outlook. The reason might be because Outlook did not subscribe to these folders.
Solution
Right click on your account name in the left bar in Outlook and select IMAP Folders…
In the IMAP Folders window, click on Query (this will request the list of folders available on the server), then select all folders (Select the first one, maintain SHIFT key on your keyboard, scroll down to the last one and click on it) and click on Subscribe.
Outlook might hang for a few seconds then click OK.
The folders will start to appear when Outlook will check for new mails.
Alternatively, you could force that process by going to Send / Receive and clicking on Send/Receive All Folder.