Migrating Thunderbird emails from MBOX to Outlook is easiest when you first convert the MBOX file into Outlook's PST format. Since Microsoft Outlook does not open MBOX files directly, using a dedicated conversion tool can simplify the process. For example, the SysInfo MBOX Converter Tool lets you add your Thunderbird MBOX files, preview the mailbox contents, and export them as a PST file. More: https://www.sysinfotools.com/recovery/mbox-converter.php