SMTP服务器需要安全连接，或者客户端未通过身份验证.服务器响应为:5.5.1需要身份验证.?8

我正在使用c#创建示例电子邮件发件人，但显示错误为:

I was create sample email sender using c# but it shows an error is:

SMTP服务器需要安全连接，或者客户端未通过身份验证.服务器响应为:5.5.1需要身份验证.

The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.5.1 Authentication Required.

        System.Net.Mail.MailMessage mail = new System.Net.Mail.MailMessage();
        mail.To.Add("toAddress@gmail.com");
        mail.From = new MailAddress("fromAddress@gmail.com", "Test Mail !", System.Text.Encoding.UTF8);
        mail.Subject = "Test Mail";
        mail.SubjectEncoding = System.Text.Encoding.UTF8;
        mail.Body = "Test message";
        mail.BodyEncoding = System.Text.Encoding.UTF8;
        mail.IsBodyHtml = true;
        mail.Priority = MailPriority.High;
        SmtpClient client = new SmtpClient();
        client.Credentials = new System.Net.NetworkCredential("myMail@gmail.com", "password");
        client.Port = 587;
        client.Host = "smtp.gmail.com";
        client.EnableSsl = true;
        client.UseDefaultCredentials = true;
        client.Send(mail);

Web配置:

<system.net>
    <mailSettings>
      <smtp from="myMail@gmail.com">
        <network host="smtp.gmail.com" password="password"
          port="587" userName="myMail@gmail.com" />
      </smtp>
    </mailSettings>
</system.net>