To open an MBOX file without using any email client, you can use MailsDaddy MBOX viewer tool. This tool allows you to open and read MBOX emails without installing Thunderbird, Apple Mail, or any other email application.
Simply launch the viewer, browse to the MBOX file, and view emails along with attachments. With the pro version, you can export emails to PDF, PST, EML, MSG etc. for easy access and backup. This method is ideal for users who only need to read or archive MBOX files without configuring an email account.