If any person wants to easily convert OST to MBOX, so try the professional conversion tool that's named eSoftTools OST to PST converter software. It can convert or repair OST files to MBOX and more formats. Help of this tool you can easily convert OST to IMAP accounts without any errors. This tool can work and supports all Outlook versions and all Windows operating systems. so first of all use the free demo version in this tool.