By default, Vuture standalone lists will not allow contacts to be added without an email address. 

If you would like to be able to add a contact without an email address to a list, you will need to contact your account manager.  They will enable the "Admin.System.Emails.Allow blank email addresses" setting and update your CSV upload in "Admin.System.Versions.CSV Upload Version 3".

Contacts will be de-duplicated based on joining up First Name, Last Name and Company.

Please note, as this is a system wide setting, once enabled it will allow contacts with blank email address fields to be added to any list throughout your instance.