wp-includes/PHPMailer/PHPMailer.php:3796Does a string contain any 8-bit chars (in any charset)?
$textstringbool public function has8bitChars($text) { return (bool) preg_match('/[\x80-\xFF]/', $text); }Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/PHPMailer/PHPMailer.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.