An Outlook PST is designed to store local copies of all your email messages, notes, contacts etc. for Microsoft Outlook. But the file can get corrupt due to several factors. To repair it, Microsoft provides Scanpst.exe also known as inbox repair tool that is automatically installed with all MS Outlook installation options depending on the operating system. It can fix several corruption issues of PST, but not all. If the file is oversized or the internal data is corrupt, the Scanpst tool will not repair. Additionally, the tool cannot serve as a workaround if the nature of corruption is severe. For these reasons, third-party tools are available that can repair a corrupted PST in all scenarios of corruption.

1. Since the file is oversized, you can use Microsoft PST Crop Tool (Pst2gb.exe) to truncate the file under 2 GB and then run Scanpst.exe utility to repair it. The PST Crop Tool truncates the file by a user-defined value and thus, some of your email messages may find missing from the resultant copy. Thus, it is suggested to backup the PST before using it.
2. You can use a third-party PST file repair utility that applies powerful scanning algorithms repair the file. The applications can fix PST corruption in all logical scenarios, when Microsoft utility cannot do so. These are specialized Inbox Repair Tool with graphically rich interface and options. Such software use safe repair techniques, basically because they are designed read-only. Thus, running the utilities causes no harm to the original emails' integrity and file structure.