woocommerce_mail_content │ filter-hook │ WC 1.0

Usage

add_filter( 'woocommerce_mail_content', 'wp_kama_woocommerce_mail_content_filter' );

/**
 * Function for `woocommerce_mail_content` filter-hook.
 * 
 * @param  $style_inline 
 *
 * @return 
 */
function wp_kama_woocommerce_mail_content_filter( $style_inline ){

	// filter...
	return $style_inline;
}

$style_inline

-

Where the hook is called

$message              = apply_filters( 'woocommerce_mail_content', $this->style_inline( $message ) );

return apply_filters( 'woocommerce_mail_content', $inlined ); // phpcs:ignore WooCommerce.Commenting.CommentHooks.MissingSinceComment

Where the hook is used in WooCommerce