The IBM Lotus Notes NSF file format is proprietary and not publicly documented.
As it changes with different releases of Lotus Notes we believe the chances of a company taking the time to create standalone 3rd party software to read it is unlikely. Especially since IBM makes it easy to access the data though an API and also provides downloads or Trial and Beta versions of the Lotus Notes Domino suite of products.
The IBM Lotus Notes .NSF file format is known as ODS which stands for On Disk Structure. There are many versions of ODS that relate to different versions of Lotus Notes. Please see the table below for an ODS Version List.
ODS Version Table
ODS Version | Lotus Notes Domino Version | Maximum Database Size |
ODS 17 | Lotus Notes 3.x | |
ODS 20 | Lotus Notes 4.x | 4Gb maximum database size. |
ODS 41 | Lotus Notes / Domino 5.x | |
ODS 43 | Lotus Notes / Domino 6.x and 7.x | 64GB or maximum allowed by the operating system |
ODS 48 | Lotus Notes / Domino 8.x | |
ODS 51 | Lotus Notes / Domino 8.5.x |