wp-includes/PHPMailer/SMTP.php:1211Send raw data to the server.
$datastring$commandstringoptional''int|bool public function client_send($data, $command = '') { //If SMTP transcripts are left enabled, or debug output is posted online //it can leak credentials, so hide credentials in all but lowest level if ( self::DEBUG_LOWLEVEL > $this->do_debug && in_array($command, ['User & Password', 'Username', 'Password'], true) ) { $this->edebug('CLIENT -> SERVER: [credentials hidden]', self::DEBUG_CLIENT); } else { $this->edebug('CLIENT -> SERVER: ' . $data, self::DEBUG_CLIENT); } set_error_handler(function () { call_user_func_array([$this, 'errorHandler'], func_get_args()); }); $result = fwrite($this->smtp_conn, $data); restore_error_handler(); return $result; }Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 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.