I have solved the issue.
I have modified the file wp-includes/registration.php
I have commented the line 143 and 144.
//if ( !$update && ! defined( 'WP_IMPORTING' ) && email_exists($user_email) )
//return new WP_Error('existing_user_email', __('This email address is already registered.') );
Now, the function wp_insert_user don’t check if the email field is empty.
Hi Clifgriffin, I have the same problem. I have two days importing users and not working well.
At least I know that is by empty email……
Have you fixed it? If I fix it, I tell you.
