You can also go for CubexSoft PST to MBOX Converter Tool for Mac OS and Windows. This software is useful; it can convert multiple Outlook emails to MBOX format along with all sending details and attachments. It is one of the most efficient utilities to export specific Outlook mailbox to MBOX file format and also convert into MBOX compatible email clients like Thunderbird, Apple Mail, Seamonkey, the Bat, Eudora etc. It was compatible with Windows OS as well as all the other operating systems. There is a free trial version of this software, users and consumers can download it without having to pay anything.