信箱不可用。服务器响应为：walauthsmtp11：主机202.142.81.4：未允许未经身份验证的中继

Question

我的邮箱位于fatcow Open Xchange服务器下。
我想从mymail@mywebsite.com向user@mywebsite.com发送电子邮件。

为此，我的代码如下：

SmtpClient smtpClient = new SmtpClient("smtp.mywebsite.com", 587);// Setting smtp client with port no, smtp server name(getting from mail central)
    smtpClient.Credentials = new System.Net.NetworkCredential("mymail@mywebsite.com", "password");//setting network credential
    smtpClient.UseDefaultCredentials = true;
    smtpClient.DeliveryMethod = SmtpDeliveryMethod.Network;
    smtpClient.EnableSsl = true;
    MailMessage mail = new MailMessage();
    //Setting From , To 
    mail.From = new MailAddress("mymail@mywebsite.com", "My NAme(sender name)");
    mail.To.Add(new MailAddress("user@mywebsite.com");
//To bypass the certificate validation
    System.Net.ServicePointManager.ServerCertificateValidationCallback = delegate(object s,
           System.Security.Cryptography.X509Certificates.X509Certificate certificate,
           System.Security.Cryptography.X509Certificates.X509Chain chain,
           System.Net.Security.SslPolicyErrors sslPolicyErrors)
    {
        return true;
    };
    smtpClient.Send(mail);

这显示错误

  

邮箱不可用。服务器响应为：walauthsmtp11：主机202.142.81.4：未允许未经身份验证的中继

所以有人可以帮助我吗？