wp-includes/PHPMailer/PHPMailer.php:4576Check whether any of the supplied addresses use Unicode in the local part.
$addressesbool protected function anyAddressHasUnicodeLocalPart($addresses) { foreach ($addresses as $address) { if (is_array($address)) { $address = $address[0]; } if ($this->addressHasUnicodeLocalPart($address)) { return true; } } return false; }Unchanged from 6.9.7 through 7.1.0.
Signature, return type and hooks compared across 3 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.