Kernel for MBOX to PST is a third-party tool designed to assist conversion of MBOX files to Outlook PST. To check the efficiency of the software, the trial version can be downloaded. It is this free MBOX to PST converter that saves the 25 items per folder in PST, EML or MSG. Once you are satisfied with the trial version of the tool user can purchase the licensed version that permits to save the MBOX mails directly to Office 365.