If you know the existing password, you can usually remove or change it through Outlook’s PST file properties. However, if the password is forgotten or Outlook is not accepting it, a dedicated PST password recovery/removal utility may be needed. SysTools PST Password Recovery Tool is one option people use to access password-protected PST files when the usual Outlook method doesn’t work. Read more : https://www.systoolsgroup.com/pst-password-remover/