title: how to send mail by using smtp in asp.net
body: <pre><code>i need solution for this error 
  </code></pre>
  
  <p>i am run that time some error occur there is:Send Email Failed.
  The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.7.0 Must issue a STARTTLS command first. i1sm8651517pbj.70</p>
  
  <pre><code>using System;
      using System.Configuration;
      using System.Web;
      using System.Web.Security;
      using System.Web.UI;
      using System.Web.UI.WebControls;
      using System.Web.UI.HtmlControls;
      using System.Net.Mail;
  
      public partial class _Default : System.Web.UI.Page 
      {
          #region  "Send email"
          protected void btnSendmail_Click(object sender, EventArgs e)
          {
              // System.Web.Mail.SmtpMail.SmtpServer is obsolete in 2.0
              // System.Net.Mail.SmtpClient is the alternate class for this in 2.0
              SmtpClient smtpClient = new SmtpClient();
              MailMessage message = new MailMessage();
  
              try
              {
                  MailAddress fromAddress = new MailAddress(txtEmail.Text, txtName.Text);
  
                  // You can specify the host name or ipaddress of your server
                  // Default in IIS will be localhost 
                  smtpClient.Host = "smtp.gmail.com";
  
                  //Default port will be 25
                  smtpClient.Port = 587;
  
                  //From address will be given as a MailAddress Object
                  message.From = fromAddress;
  
                  // To address collection of MailAddress
                  message.To.Add("muthu17green@gmail.com");
                  message.Subject = "Feedback";
  
                  // CC and BCC optional
                  // MailAddressCollection class is used to send the email to various users
                  // You can specify Address as new MailAddress("admin1@yoursite.com")
                  message.CC.Add("muthu17green@gmail.com");
                  message.CC.Add("muthu17green@gmail.com");
  
                  // You can specify Address directly as string
                  message.Bcc.Add(new MailAddress("muthu17green@gmail.com"));
                  message.Bcc.Add(new MailAddress("muthu17green@gmail.com"));
  
                  //Body can be Html or text format
                  //Specify true if it  is html message
                  message.IsBodyHtml = false;
  
                  // Message body content
                  message.Body = txtMessage.Text;
  
                  // Send SMTP mail
                  smtpClient.Send(message);
  
                  lblStatus.Text = "Email successfully sent.";
              }
              catch (Exception ex)
              {
                  lblStatus.Text = "Send Email Failed.&lt;br&gt;" + ex.Message;
              }
          }
          #endregion
  
          #region "Reset"
          protected void btnReset_Click(object sender, EventArgs e)
          {
              txtName.Text = "";
              txtMessage.Text = "";
              txtEmail.Text = "";
          }
          #endregion
      }
  </code></pre>