wp-includes/PHPMailer/SMTP.php:1431Enable or disable use of SMTPUTF8.
$enabledbooloptionalfalse public function setSMTPUTF8($enabled = false) { $this->do_smtputf8 = $enabled; }Unchanged from 6.9.7 through 7.1.0.
Signature, return type and hooks compared across 3 parsed releases.
src/wp-includes/PHPMailer/SMTP.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.