OST To PST Converter

You can try this:
www.ost2.com
and
http://microsoft-ost-to-pst-converter-free-software.en.softonic.com/

But have you tried importing the ost into outlook?
https://support.office.com/en-us/article/Open-or-import-items-from-an-offline-Outlook-Data-File-ost-A584963E-A66D-4D9D-8845-31CB270F6880

You can try a manual technique here to convert an OST file into PST format. To perform conversion of OST to PST follow the steps mentioned below and before using the steps make sure, Outlook application is installed and is running on your local machine.

1. Run MS Outlook application.

2. From the main menu, go to File

3. Choose ‘Import and Export’ or you may also press‘t’ on the keyboard.

4. Select ‘Export to a file’, click on Next.

5. Choose Personal File Folder (.pst) and move further by clicking on Next.

6. One by one select all the items that you may want to export.

7. Save all the above selected email items to a specific location of your choice.

8. Click on Finish to end the conversion process.

You may also get help from this OST to PST conversion solution which lets you to restore OST files to a Live Server or convert them to new PSTs or add to existing PSTs.

Hope this helps!

None of them are freeware but yes, every tool allows you save some data without even registering, So you can try the demo version if demo version fills you need

http://www.ost2.com/ free for saving some amount of data, rest register for full version
http://www.stellarservertools.com/ost-pst-converter.php free to save & convert 20 items per folder, rest purchase the software
And some more choices http://www.thetoptens.com/microsoft-ost-pst-conversion-tools/

Better to go for good rather than low cost, low performing software.

This was the Cheapest and worked Great for all mailboxes

Try this tool its really good while converting your mails one format to another format for more details please visit : https://www.softknoll.com/ost-to-pst-converter/

I found best solution and suggest to use try  visit: Best way to export OST file to office 365 & Live Exchange Server

in order to use third party OST to PST converter tool, this tool recover deleted mails item and repair corrupt OST file with Export OST to PST, office 365 and live Exchange server.

more info: OST to PST Converter

Hello,

I would like to suggest you that if your OST file has been corrupt or inaccessible than you can go for a simple way to convert corrupted or inaccessible OST file into PST format. You can try any affordable OST to PST Converter tool from RecoveryMails. I suggested you this software because i have already used this software to convert my OST Mailbox file.

http://www.recoverymails.com/convert-ost-to-pst.html

You should try helpful and most reliable solution available in the google i.e, KDETools OST to PST Converter that allow to Convert multiple OST files into 20+ different file format such as:

• OST to PST in Outlook
• OST to Gmail
• OST to Exchange Server
• OST to Office 365
• OST to Windows Live Mail
• OST to Yahoo Mail
• OST to Godaddy Mail
• OST to Hostgator
• OST to Apple pour MAC
• OST to Thunderbird

Click to download totally free: https://www.kdetools.com/ost-to-pst-converter.html

vMail OST to PST Converter is an another easy to use tool to convert Outlook data files from OST to PST format and export all emails, contacts, calendars, tasks, notes, journals, etc. This software is also helpful in Outlook data migration from OST file to Office 365, Exchage Server and Gmail / G Suite.

Learn More- OST to PST Converter