Now there is a free solution available for users to convert NSF to MBOX called
eSoftTools NSF to MBOX Converter software. It is a reliable software to be used by both technical and non-technical people to perform the operation of NSF file conversion. Without any tension, you can convert NSF file to MBOX with 100% accuracy. Also, you can easily export emails from any size NSF file to MBOX. Moreover, free demo is available and it supports all Windows versions including 11, 10, 8.1, 8, 7, Vista, XP, and other versions.
Read more- Convert NSF to MBOX