此代码自一年以来一直有效，但今天突然停止工作。我没有更改gmail密码或任何东西。 gmail有更新吗？ 我该如何解决这个问题？

错误： 无法发送消息。邮件程序错误：SMTP 错误：无法验证。

 require_once '../db/config.php';
    use PHPMailer\PHPMailer\PHPMailer;
    use PHPMailer\PHPMailer\Exception;


function send_email($email, $code) {
    require_once '../ml/PHPMailer/PHPMailer.php';
    require_once '../ml/PHPMailer/SMTP.php';
    require_once '../ml/PHPMailer/Exception.php';

$mail = new PHPMailer(true);

try {
        $mail->isSMTP();                                         
        $mail->Host       = 'smtp.gmail.com';                   
        $mail->SMTPAuth   = true;                                
        $mail->Username   = 'example@gmail.com';            
        $mail->Password   = 'aaaabbbbb';                    
        $mail->SMTPSecure = PHPMailer::ENCRYPTION_STARTTLS;       
        $mail->Port       = 587;                                   

        //Recipients
        $mail->setFrom('example@gmail.com', 'mycompany');
        $mail->addAddress($email); 
        $mail->addReplyTo('example@gmail.com', 'mycompany');


        // Content
        $mail->isHTML(true);                      
        $mail->Subject = 'Verification code';
        $mail->Body    = 'Use the verification code to activate your account.
 '.$code.'';
        $mail->AltBody = 'Use the verification code '.$code.' to activate your account';

        $mail->send();
        echo 'Verification code has been sent to your email '.$email;
    } catch (Exception $e) {
        echo "Message could not be sent. Mailer Error: {$mail->ErrorInfo}";
    }
}