If you want to open NSF file in Thunderbird, then I suggest you download SysInspire NSF to PST converter software. This tool has many functions that can help users in conversion. It can convert NSF file into multiple file format such as NSf to PST, EML,EMLX, Office 365, Yahoo Mail, HTML, Gmail. Etc. it has a demo version that can allow users to convert 25 items from each folders. It has a PST splitting option users can split PST file into multiple small sizes. It has technical support and all users can get help by mail or live chat. It supports all versions of Windows OS, even it can support all versions of lotus Notes.