As you know, OST is a general Outlook mailbox file, which stores all email data in a concatenated format, and these files get corrupted easily. To avoid any kind of data loss, many times users want to convert OST files to PST format, which is understood more secure file format than OST files. In this regard, one tool hits my mind, i.e., TrustVare OST to PST Converter. This utility allows users to convert OST files to PST format with the entire mailbox data and attachments. The software kept intact all email formatting and original folder hierarchy throughout the conversion process. It can convert highly corrupted, orphaned, damaged, or inaccessible OST files to PST format. Try the freeware version to know how it works. Refer: https://www.trustvare.com/ost/pst/