Most people who've had experience dealing with Microsoft Outlook errors and OST corruption know for a fact that converting OST to PST isn't that easy. First let's look at the need for such a conversion and then some of the options we have to accomplish the same. When does OST to PST Conversion becomes necessity ? Synchronization Issues: When there is some connectivity issues between Outlook and the Exchange it could lead to synchronization issues that could make the OST file inaccessible. Corrupt OST Files: The OST corruption can also result in many issues that could potentially lead to loss of data and information. Some methods for OST to PST Conversion Drag and Drop in Outlook You can simply drag and drop mailboxes in Outlook to achieve OST to PST Conversion. This could sound really simple but is really time consuming and unintuitive for large files. Outlook Import/Export Wizard Use Outlook Import/Export Wizard as specified in the steps below to achieve conversion of OST to PST. Open Outlook Go to File -Open and Export- Import/Export Select "Export to a File" from the window that opens and click on Next. Select Outlook Data File(.pst) and proceed. Select the location where you want to keep the PST files. There is no guarantee that this method will work especially if the OST heavily corrupted. Using a professional OST to PST Converter While there are plenty tools in the market that can help achieve this, the only one that really stands out is EdbMails OST to PST Converter tool. It can export your mails, contacts, journals, notes, calendars etc and save them into PST files. It supports most versions of Windows and Exchange servers and also direct migration to Office 365 and Live exchange server.