If you want to Open the NSF file in Thunderbird without losing any data. So I recommend you use the SysInspire NSF to PST Converter Software. Because it is especially designed to recover, convert, and repair NSF files. Using this software you can easily convert Lotus Notes NSF files to MBOX. After conversion, you can eisly open the NSF file in Thunderbird without any errors.

Read more:- https://www.sysinspire.com/blog/how-to-open-nsf-file-in-thunderbird/