Hi Romina,

By default, there is no email for that. 

However, you can add one using this PHP code snippet:

add_action('b2bking_reject_user_admin_before_delete', function($user_id){
    $user = new WP_User($user_id);
    $user_email = $user->user_email;
    $message = 'Thank you, but you are not eligible for our B2B program...';
    do_action( 'b2bking_new_message', $user_email, $message, get_current_user_id(), 0 );
}, 10, 1);

You can set the $message to anything you'd like in the above snippet.

Kind regards,

Stefan