NSF to MBOX Converter Tool is another significant and result-oriented application that can ease your work by performing migration of Lotus Notes file to Mozilla Thunderbird and some other file formats and email clients. The application has a competence to migrate Notes MBOX file and its associated data items and move them to PST, MSG, EML, EMLX, MBOX, HTML, etc.
Refer:
https://www.gaintools.com/nsf/mbox/