Outlook Data File IMAP Folder Items are Missing because of Filter
When you open a PST Data File in Outlook, you’ll find that the folders are empty, they have the contents of an IMAP mailbox, probably if you try to move the folders to a new Exchange or Office 365 mailbox.
If the IMAP folders not showing Items, after copying/moving or after importing messages from an existing IMAP account or from a opened Outlook PST Data File, then follow this tutorial to fix the issue in Outlook 2019, 2016 or 2013:
Open Outlook Data File via File – Open & Export – Open Outlook Data File.
The content of the Outlook Data File (PST), doesn’t show items.
Outlook Doesn’t Show Imported Items
When you watch items in the WebApp (WebMail), you can see the folders with content, but the same content can’t be found in the Outlook folders, you may notice that in Outlook when you select a folder, at Outlook status bar appears FILTER APPLIED instead the number of items. The conclusion is that the contents of the folder with the items are hidden.
If FILTER APPLIED in the Outlook status bar does not appear, the Filter is unchecked, to enable Filter right-click in the status bar and check Filter.
How to FIX show hidden Items
Now with Filter applied in the status bar, just click to FILTER APPLIED which opens the Filter window.
Go to the Advanced section and click the Remove button, the IMAP-Status entry will be removed, then click Clear All and OK.
Outlook folders of the PST data file now appear with content.