Last Updated on June 26, 2021
OST file is automatically created when we connected MS Outlook client to MS Exchange Server. OST (.offline storage table) files allow users to work in offline mode, that is, when there is less or no network connectivity available. And when network connection gets connected, OST files get synchronized with the user mailbox on MS Exchange Server. To migrate OST file out of MS Exchange Server environment, manual conversion from OST to PST has to be performed such that all the mail items including Inbox, Outbox, Sent Items, Contacts, Calendar Entries, Tasks, Journals, Posts, Appointments, Drafts, Meeting Requests, and Notes, etc. can be accessed without connecting to MS Exchange Server.
Need for performing manual OST to PST conversion occur in case user’s account on MS Exchange Server got accidentally deleted or corrupted, MS Exchange Server downtime, Server crash, database corruption and more etc.
Note: Be assure before performing manual OST to PST conversion process, MS Outlook must be installed on the local computer system connected to MS Exchange Server.
Now follow the steps to Convert OST to PST file manually
(I assume we are using MS Office 2003 Professional Edition):
- Open MS Outlook
- Click the File menu.
- Select the “Import and Export” wizard or press ‘t’.
- From the list, click the “Export to a file” option and then click Next button.
- Select Personal File Folder (.pst) and then click Next button.
- Selected items to be exported or Click on parent root and check the Include sub-folders option.
- Browse and select the target folder for saving the email items.
- Click the Finish button.
We perform OST to PST Conversion task manually;
it is only be possible when user is connected to MS Exchange Server. And when the user gets disconnected from MS Exchange Server or in case MS Exchange Server got damaged, then you need a third party application to perform OST to PST conversion process.
If the above process did not help you or you are unable to perform such operation, In that case I would recommend user to try the Free Trial version of OST to PST Converter software. In Free version you can repair ost file if it is corrupted and convert ost to pst emails. And recovered or Converted emails you can see in preview items but you cannot saved it. If you are completely satisfied with software capability, you need to purchase the software license.
You can download this software from here: 
Exchange Server Helping Tips 
Can you give the steps to do this for Office 2013? Office 2003 is quite old.
Instantly convert OST file to PST file in just few clicks. Go through Free version to Convert OST file.
I had used this tool and got satisfactory results.
http://www.osttopstconverter-tool.com/
Regain OST to PST Conversion Software and easily recover corrupted OST data and convert into Outlook PST format with all Emails,Send Items, Contacts, calendar , Notes, entries, and journals.It has complete solution to import OST files into PST with all emails item.It gives you authority to see preview of their recovered OST files before conversion and convert them into new readable PST files without facing any problems.With the help of this software users can smartly recover their corrupt OST file and successfully convert OST data into PST data format.
http://www.ostintopstconverter.com/
All the time manual process did not work and some times it is risky as well. Minor mistake may harm your file. And sometime OST file is corrupt and manually it is not easy to repair OST file. Third party tool will charge you a little amount and also reduce the 80% of headache. Use this tool to convert OSt file.
https://www.regainsoftware.com/ost-to-pst-converter.html
Thank you for your step by step guide for Converting OST file to PST file. This guide helped me to convert my OST file to PST.