不允许使用邮箱名称

Question

使用“system.net.mail”发送测试电子邮件时遇到问题。每次按下提交按钮时出现错误消息“邮箱名称不允许。服务器响应为：5.3.0中继拒绝检查邮件”。提前谢谢。

Code_behind：

public class MailHelper
{
    public static void SendMailMessage(string from, string to, string bcc,
        string cc, string subject, string body)
    {
        MailMessage mMailMessage = new MailMessage();
        mMailMessage.From = new MailAddress(from);
        mMailMessage.To.Add(new MailAddress(to));
        if ((bcc != null) && (bcc != string.Empty))
        {
            mMailMessage.Bcc.Add(new MailAddress(bcc));
        }
        if ((cc != null) && (cc != string.Empty))
        {
            mMailMessage.CC.Add(new MailAddress(cc));
        }
        mMailMessage.Subject = subject;
        mMailMessage.Body = body;
        mMailMessage.IsBodyHtml = true;
        mMailMessage.Priority = MailPriority.Normal;

        string smtpServer = "";
        //Read the Web.config to get configuration setting
        smtpServer=System.Web.Configuration.WebConfigurationManager.AppSettings["smtp"];
        // Instantiate a new instance of SmtpClient
        SmtpClient mSmtpClient = new SmtpClient(smtpServer);
        // Send the mail message
        mSmtpClient.Send(mMailMessage);
    }       
}

Web_config：

<appSettings>
<add key="smtp" value="smtp.mydomain.com"/>
</appSettings>
<system.net>
<mailSettings>
<smtp from="defaultEmail@mydomain.com">
<network host="smtp.mydomain.com" port="25" userName="yourUserName" password="yourPassword"/>
  </smtp>
</mailSettings>
</system.net>

Sumbit_Click：

 protected void Sumbit_Click(object sender, EventArgs e)
    {
        MailHelper.SendMailMessage("from@email.com", "to@email.com", null, null,
            "subject", "textEnquiry.Text");
    }