Here’s a sample code for getting and saving the assigned client’s email as well as adding a new email meta tag.

Paste this code on your active theme’s functions.php file.

function save_assigned_client_email_callback($shipment_id) {
    $assigned_client_id = get_post_meta($shipment_id, 'registered_shipper', true);
    $args = array(
        'include' => [$assigned_client_id],
        'fields' => ['user_email'],
    );
    $email = get_users($args)[0]->user_email;
    update_post_meta($shipment_id, 'client_reg_email', $email);
}
add_action('after_wpcfe_save_shipment', 'save_assigned_client_email_callback', 10, 2);
function add_assigned_client_email_metatag( $tags ){
    $tags['{client_reg_email}'] = 'Client Registered Email';
    return $tags;
}
add_filter( 'wpc_email_meta_tags', 'add_assigned_client_email_metatag' );

After pasting and saving the code, refresh your wordpress dashboard then navigate to WPCargo -> Client Email Settings and as you scroll down , you will see that a new email meta tag called “client_reg_email” will appear.

Copy the email meta tag and paste it on the “Mail To:” field and hit Save.