Thank you for the useful information! If you needed to transfer emails from the old mail client to Outlook, you will need to package the emails in a file with the MBOX extension. How to open mbox files? In this article https://www.outlooktransfer.com/how-to-open-mbox-file/ you will find a complete guide. It will help you to export all emails to Outlook using the application from GlexSoft. If you don't want to lose important information, use our software!