The manual method is here that user can export PST to MBOX file format by using KDETools PST to MBOX Converter. This software is one of the most popular email clients that supports more than 20 email clients. The converted PST file can be saved in many other file formats including MBOX. Other formats that PST data can be saved in are EML, EMLX, MSG, HTML, etc. Deleted items recovery is possible with the tool.