If you have NSF files and wants to open them in Outlook 2021, 2019, 2016 and all below versions then you can not directly do so. Until or unless you convert them into PST format. In this situation, You can take help of most trust-worthy ZOOK NSF to PST Converter software. It is developed with highly advanced algorithm which makes it possible in transferring of data from
NSF to PST file format including emails, contacts, calendars, attachments, tasks, journals, etc. It is capable to recover data from inaccessible, corrupted or orphaned NSF files to PST format. After converting NSF files to PST, Users can open view resultant PST files in any versions of Outlook and you can also customize them based on size. It is Windows supported platform thus you can run this tool on any Windows supported platform.
For more info-
https://www.zooksoftware.com/nsf-to-pst/