Mac Mail email client supports MBOX file so it easy to import them manually. Just go to the File Menu then choose Import Mailbox . Now window of Import will pop up in which you have to choose the radio button of Files in Mbox format and then Continue . After that select the location of file and then click on choose button. Once you follow all the mention steps you are able to view MBOX files in Mac Mail email client. For the user reliability if you want to view the above steps with screenshot then visit Lotus Notes to Apple Mail Tool to Import NSF Emails to Mac Mail