You must have to rescue .nsf files if you want to regain your e-mails and contacts that you have lost through IBM Lotus Notes. It is a database system for the IBM server platform which also acts as an e-mail client, You can send and receive emails through contacts, add attachments, create journals and notes and all the possible work that can be done by an e-mail client. Like any other e-mail application it also has its own database, and if this database become corrupted and affected by any other means then the operation of Lotus notes will be hampered and you have to rescue .nsf file which is the database file. The database file can get corrupted if it is infected by virus or it is handled in any improper way. You may not be able to access you emails,send or receive new ones. You can repair the database by any inbuilt tool or you may have to reinstall the application but all the database item in the .nsf file will be deleted. But don't worry you can rescue .nsf file items using NSF recovery software. It will scan the system storage media for the lost and deleted database items and then recover them in the .nsf database file.