woocommerce_email_content_type filter-hook . WC 1.0

Usage

add_filter( 'woocommerce_email_content_type', 'filter_function_name_3144', 10, 3 );
function filter_function_name_3144( $content_type, $that, $default_content_type ){
	// filter...

	return $content_type;
}

$content_type

-

$that

-

$default_content_type

-

Where the hook is called

return apply_filters( 'woocommerce_email_content_type', $content_type, $this, $default_content_type );

Where in WP core the hook is used WooCommerce