Mozilla Thunderbird is an open source email client that provides data in MBOX and Maildir file format. But user can't import Thunderbird data to Outlook directly.

MailsDaddy Thunderbird to Outlook Converter tool is the best GUI based application to move bulk Thunderbird MBOX and Maildir files to Outlook and others. The application has various other export options like EML, MSG, HTML, MHTML, and RTF file formats. You can install the solution in any Windows OS and easily move the mailbox from Thunderbird to PST format. The free demo edition of the software exports up to 20 emails from each folder.

Read more: Thunderbird to Outlook Conversion