To remove a forgotten password from a PST file, you typically need to use third-party software specifically designed for this purpose, as Microsoft Outlook does not provide a built-in feature for password recovery. Other than that you can also use the Advik PST Password Remover tool that have techniques to decrypt the PST file and remove or recover the password. One common method involves brute-force or dictionary attacks to try different combinations of characters until the correct password is found. However, it's important to note that the success of password removal depends on factors such as the complexity of the password and the strength of the encryption used in the PST file. Additionally, it's crucial to ensure that you have the legal right to access the PST file without the password, as attempting to remove passwords from files without proper authorization may violate privacy or security policies. Always exercise caution and use such tools responsibly and ethically.