Disabled 2 email option from additional Billing address

You can customize the WooCommerce address fields and not include the billing email if it is a secondary address with this customization. This will remove the field and it will no longer run validation.

This customization should do that:

add_filter( 'woocommerce_billing_fields', function ( $fields ) {
	if ( isset( $fields['billing_email'] ) && ! empty( $_GET['address-book'] ) ) {
		unset( $fields['billing_email'] );
	}
	return $fields;
} );

Depending on what you are trying to do, if you just didn’t want to have customers re-enter email, I would probably do something like this and have it automatically fill out the form with the user’s email address by default.

add_filter( 'woocommerce_billing_fields', function ( $fields ) {
	if ( isset( $fields['billing_email'] ) ) {
		$current_user = wp_get_current_user();
		if ( ! empty( $current_user ) ) {
			$fields['billing_email']['default'] = $current_user->user_email;
		}
	}
	return $fields;
} );

Hi, Matt Harrison?

Thank you for this solution it’s working for me.