For converting OST to PST, you definitely need to use EdbMails. This high performance and fast utility offers you tons of features at an incredibly low price. Let's see the features of it.
100% highly secure for recovering OST from all types of corruptions
Convert OST to commonly used formats such as HTML, EML and MHT
PST file split option to split the target PST into smaller chunks
Completely maintains one-one folder structure on both source and target
Possible to convert large or oversized OST file with no limitations
Easily recover and convert permanently deleted mail items
Breathtaking UI similar to that of MS Outlook
Cloud based direct migration to Office 365/live Exchange server
Convert password protected OST files without requiring a password
30 days money back guarantee with 24/7 live customer support
The Free Trial version converts 30 mail items from every folder and allows you to test all the features.