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Open the Windows Registry Editor by pressing the Windows key + R, typing "regedit" in the Run dialog box, and hitting Enter.
Navigate to the following registry key:
HKEY_CURRENT_USER\Software\Microsoft\Office\XX.0\Outlook\PST
Replace "XX.0" with the version number of Outlook you are using. For example, for Outlook 2019, the version number would be "16.0".
Right-click on the "PST" key and choose "Export" to create a backup of the key.
After creating the backup, delete the "PST" key from the registry.
Note: Deleting the "PST" key will remove all previously saved Outlook passwords from the registry.
Close the Registry Editor.
Restart Outlook.
When prompted for the password to access the PST file, leave the password field blank and click "OK" or "Cancel".