You can go with this OST to PST Converter Open Source that can easily convert Contacts, Calendar Entries, Journals and Notes along with Emails from OST to PST without any hassle. This OST to PST Open Source allow the users to select the convertible OST files which you want to convert. OST to PST Convert enable the users to Convert OST files to PST and other formats such as MBOX, PDF, DBX, EML, MSG file and Office 365 format.  It also allow the users to export OST to Office 365 and Live Exchange Server. It also enable the users to split large PST files into Small PST files without any data loss.

After Conversion, OST to PST Converter ask the users to select the destination location to save converted OST files. It GUI is simple and user friendly and allow all users both technical or non technical can easily use this software without have any technical skill. I would like to suggest you to use it free demo version to learn more about it features and functions.