Hi, it is highly recommended to use the well-known and trusted solution to convert PST to MBOX file format. You can try one of the best Outlook PST file converter (https://www.data-recovery-solutions.com/outlook-pst-file-converter.php) tool available in the market. The automated third-party solution can easily export PST files to MBOX, EML, EMLX, PDF, etc. The free version allows exporting 50 emails for free. ‎

For the conversion of OST to PST, you can try OST to PST converter online Software which is an efficient way to migrate OST files to Outlook PST format. Through this third-party tool that smoothly recover corrupt OST files and also export several files into multiple file formats such as-PST, Zimbra, Live Exchange Server, Gmail, Office 365, MBOX, EML, EMLX, MSG, vCard, ICS, and etc. Along with it also show & manage all emails properties or mailbox attachments such as- Show the preview of all OST emails including these items: Messages Attachments Embedded Images HTML Formatting Attachments Header's Details Contacts Calendar Tasks Notes Journal and etc. The software supports all the version of MS Outlook. 

•    Download, install and run OST to PST Converter.
•    Click on the "Open" button to load OST file.
•    There are two options to browse OST file(s).

 Add File: To select OST file one by one.
 Add Folder: To select folder of OST files.

The steps to export the OST files to PST Outlook:
1.    Open Microsoft Outlook.
2.    Click File menu and select 'Open & Export' and click on Import/Export from the available options.
3.    From the Import and Export, click Export to a file and select the file format option – PST from the suggested storage options.

Click here for more info:- https://www.kdetools.com/how-to/convert-ost-to-pst-without-outlook.html

• Export OST files with attachments into PST format
• Easily Select OST files with Drag and Drop option facility
• Choose output location to save converted OST files
• Supports to move OST to PST without Outlook
• Operable with all new or old versions of MS Outlook
• Preserves OST file integrity and folder structure during migration

Know more: http://dailygram.com/index.php/blog/466237/best-ost-to-pst-converter/

Is your OST file inaccessible, Need to transfer OST file from one computer to another? Want to convert OST file to PST? If the answer to any of the above question isyes, then look no further. With the help of V sodtware OST to PST Converter, you can easily convert an OST file to PST format and seamlessly transfer the OST file data to whichever computer you wish to. Vmail OST to PST Converter quickly converts all the OST data including emails, contacts, calendars, notes & Journals withoutdamaging the structure of the OST file.
View Details http://www.vsoftware.org/buy-ost-to-pst-converter.html