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Through my testing of importing a .pst file into Classic Outlook, a progress box appears during the process. Once the import is complete, the progress box disappears. However, in some cases, the mailbox may not immediately appear because the import finishes very quickly.
After the import, the data will appear in the corresponding folders based on their original dates. You may need to scroll through the folders to confirm that the items were imported correctly.
If you prefer to open the .pst file in a separate folder, you can use the Open Outlook Data File option and compare the data with the folder where you previously imported the file.
Reference: Open and close Outlook Data Files (.pst) - Microsoft Support
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