Download this free tool of eSoftTools name as NSF to PST Converter Software by which you can simply perform the conversion task of Lotus Notes NSF file to a working PST file. It will simply Export all your important databases of Lotus Notes NSF file such as- emails, contacts, tasks, notes, journals, appointments, etc to various readable file formats. For a quick demo of all its features, users can download a free trial version of this software from the given link.
Know More:- Convert NSF to PST
You can also try this way-
Open the NSF file (you want to export in PST format) in Lotus Notes email client. Open the Mailbox >> click on File Menu >> click on Export option. Suggest a saving name to the NSF file and choose CSV (Comma Separated Value) option from file saving format.
I hope this will help