WordPress at a glance
filter is not described

woocommerce_mail_callback_params filter-hook . WC 1.0

Usage

add_filter( 'woocommerce_mail_callback_params', 'filter_function_name_5240', 10, 2 );
function filter_function_name_5240( $array, $that ){
	// filter...

	return $array;
}
$array
-
$that
-

Where the hook is called

WC_Email::send()
woocommerce_mail_callback_params
woocommerce/includes/emails/class-wc-email.php 652
$mail_callback_params = apply_filters( 'woocommerce_mail_callback_params', array( $to, $subject, $message, $headers, $attachments ), $this );

Where in WP core the hook is used WooCommerce

Usage not found.