wp-includes/PHPMailer/PHPMailer.php:1447Tells whether IDNs (Internationalized Domain Names) are supported or not. This requires the intl and mbstring PHP extensions.
bool public static function idnSupported() { return function_exists('idn_to_ascii') && function_exists('mb_convert_encoding'); }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.