WordPress at a glance
filter is not described

comment_notification_headers filter-hook . WP 1.5.2

Filters the comment notification email headers.

Usage

add_filter( 'comment_notification_headers', 'filter_function_name_6246', 10, 2 );
function filter_function_name_6246( $message_headers, $comment_id ){
	// filter...

	return $message_headers;
}
$message_headers(string)
Headers for the comment notification email.
$comment_id(int)
Comment ID.

Where the hook is called

wp_notify_postauthor()
wp-includes/pluggable.php 1568
$message_headers = apply_filters( 'comment_notification_headers', $message_headers, $comment->comment_ID );

Where the hook is used (in WP core)

Does not used.