SMTP错误:无法进行身份验证.SMTP连接(）失败.PHPMailer

我正在编写一个电子邮件函数，用于用PHP向许多收件人发送时事通讯。

<?php
  require_once('class.phpmailer.php');
  require_once('class.smtp.php');
  $mailer = new Mailer();
  Class Mailer{
    function __construct(){
      $dbCon = mysqli_connect("localhost", "root", "", "dbppa");
    }

    public function sendMail($e,$message,$subject){
        $mail = new PhpMailer;
        $body = $message;
        $subject = "PPA Newsletter";
        $clientName = $e;
        $mail->SMTPDebug = 2;
        $mail->CharSet = 'utf-8';
        $mail->isSMTP();
        $mail->SMTPAuth = true;
        $mail->Host = 'tls://smtp.gmail.com:587';
        $mail->Port = 587;
        $mail->Username = "myemail@mail.com";
        $mail->Password = "password";
        $mail->SMTPSecure = 'tls';
        $mail->setFrom("myemail@mail.com","PPA Administrator");
        $mail->addReplyTo('myemail@mail.com', 'PPA Admin');
        $mail->Subject = $subject;
        $mail->AltBody = "This is the official news letter from PPA ";
        $mail->Body = $body;
        $address = $e;
        $mail->AddAddress($address, $clientName);
        if(!$mail->Send()){
            echo "NOT SENT";
        }
        else{
            echo "SENT";

        }

    }
  }//class mailer
?>

在上面给出的代码中。我提供了正确的电子邮件用户名和电子邮件密码。来自Gmail。但它不会将给定的电子邮件发送给收件人。它总是返回SMTP错误的ErrorInfo：

Could not authenticate. SMTP connect() failed. 

为什么？请帮忙。