The problem is likely to be caused by corrupted OST files, and various other reasons.
Try one of the following suggestions to fix the issue.
The content and emails in the mailboxes are not refreshed, i.e.
only the old emails are shown, and new emails are not downloaded to Outlook, even though the status bar stated that the folder is updated.
The command for the manual update procedure can be found here: Outlook will automatically download updates only unless the size of the changes is larger than 12.5% (one-eighth) of the total OAB size.
You can also check the status of the Exchange server by contacting your Exchange server administrator.
Outlook Recovery Toolbox saves the recovered information in a new PST file or in several files, each one being maximum 1 Gb large.
The folder structure of new PST files is similar to the original data structure of the damaged files.
When you have Cached Exchange Mode enabled, Outlook by will by default cache the main Global Address List as well.
This is called the Offline Address Book and is being generated on the Exchange server.