我想從我的應(yīng)用程序發(fā)送電子郵件，并且我編寫了以下代碼來發(fā)送郵件    MailMessage msg = new MailMessage();    msg.From = new MailAddress("mymailid");    msg.To.Add("receipientid");    msg.Subject = "test";    msg.Body = "Test Content";    msg.Priority = MailPriority.High;    SmtpClient client = new SmtpClient();    client.Credentials = new NetworkCredential("mymailid", "mypassword", "smtp.gmail.com");    client.Host = "smtp.gmail.com";    client.Port = 587;    client.DeliveryMethod = SmtpDeliveryMethod.Network;    client.EnableSsl = true;    client.UseDefaultCredentials = true;    client.Send(msg);我在本地主機(jī)上運(yùn)行它，所以我在發(fā)送它時(shí)犯了什么錯(cuò)誤。當(dāng)我發(fā)送按鈕時(shí)，它給出了類似的錯(cuò)誤SMTP服務(wù)器需要安全連接，或者客戶端未通過身份驗(yàn)證。服務(wù)器響應(yīng)為：5.5.1需要身份驗(yàn)證。Web.config文件中的代碼 <appSettings>    <add key="webpages:Version" value="2.0.0.0" />    <add key="webpages:Enabled" value="false" />    <add key="PreserveLoginUrl" value="true" />    <add key="ClientValidationEnabled" value="true" />    <add key="UnobtrusiveJavaScriptEnabled" value="true" />       <add key="smtpServer" value="smtp.gmail.com" />    <add key="EnableSsl" value = "true"/>    <add key="smtpPort" value="587" />    <add key="smtpUser" value="sender@gmail.com" />    <add key="smtpPass" value="mypassword" />    <add key="adminEmail" value="sender@gmail.com" />  </appSettings>  <system.net>    <mailSettings>      <smtp from="sender@gmail.com">        <network host="smtp.gmail.com" password="mypassword" port="587" userName="sender@gmail.com"  enableSsl="true"/>      </smtp>    </mailSettings>  </system.net>我該怎么做才能解決此錯(cuò)誤并發(fā)送郵件？