Before you can purchase any paid software for NSF to PST conversion, you can try an easy manaul trick here. Though the manual trick doesn't convert NSF database into PST format, but you can export NSF data into such format which is supported by Outlook client. All you need to do is:
  • First export NSF files' data into Comma Separated Value or Structured Text format by using Lotus Notes' Export feature.
  • Then you can import the new file to MS Outlook by using Outlook's Import feature.

For complete information, you can read this blog post: wordpress.semnaitik.com/2014/04/17/convert-nsf-to-pst-format/

I hope it would be helpful here.

Thanks and best regards.