In v3, users were not able to Import from CSV File if an email field/cell was left blank in the CSV file. I was able to successfully import a CSV file in v4 from the Email Invitations List with one contact (Michelle Aspesi) which had only a first and last name listed and no email address.

Also, I tried importing a different list twice that had four contacts and both times were successful. Duplicate contact data was imported. Attached is that csv file with the four contacts. Also attached is my Email Invite List after importing various csv files. You'll see duplicate info and blank info.

This is in event #178, Luau For Life