Notes about the NS4 file extension:
To open this file type, a required software must be installed. Without it you only see a Windows message "The following file cannot be opened
" (Windows 7) or "How do you want to open this file?
" (Windows 10) if you double-click the file. There click on "More apps"
and choose a suitable software to view such files on your PC or from email attachments.
The NS4 file type is primarily associated with 'Notes' by IBM. This was a Lotus product. Lotus was bought out by IBM. Lotus Notes and Domino are a fundamental component of IBM Workplace
Detailed information for file extension NS4:
Primary association: Notes
Mime type: application/vnd.lotus-notes
To change file associations press Windows Key
and then Apps and Features
> Default apps
> Choose default apps by file type
Invalid file associations could be the result of underlying issues within your Windows PC.