If you need to convert offline OST to Outlook PST, then use eSoftTools OST to PST Converter. You can convert multiple OST files to PST format without creating any error. The software can provide the highest level of security. During the conversion process, it can preserve all emails properties and data like contacts, calendars, emails, attachments, etc. This application works with all versions of Windows OS and MS Outlook 2003, 2007, 2010, 2013, 2016, and 2019.
Get more info- convert offline OST to Outlook PST
Convert OST to PST Manually
Open Outlook and go to the File menu.
Select the Import/Export option.
Choose Export to a file.
Select Outlook Data File (.pst)
Choose whether to export a specific folder or the whole account.
Check the Include subfolders box.
Next, select a destination for the Export, and then click Finish.
Regards,
Peter