Notes Storage Facility
From Just Solve the File Format Problem
Notes Storage Facility (NSF) is used in Lotus Notes, Lotus Domino, and the later versions called IBM Notes and IBM Domino, to store e-mail, contacts, appointments, notes, and other things. It is structured as a collection of items called "notes" with data and metadata on each.
Currently owned by HCL
File identification
Files start with the hex bytes 1a 00, often followed by 00 03 00 00 or 00 04 00 00.
