title: 5.7.57 SMTP - Client was not authenticated to send anonymous mail during MAIL FROM error
body: <p>I have to send mails using my web application. Given the below code showing <code>The SMTP server requires a secure connection or the client was not authenticated. The server response was:</code> </p>
  
  <blockquote>
    <p>5.7.57 SMTP; Client was not authenticated to send anonymous mail during MAIL FROM.</p>
  </blockquote>
  
  <p>Help me to find a proper solution. Thank you.</p>
  
  <p><strong>Code:</strong></p>
  
  <pre><code>protected void btnsubmit_Click(object sender, EventArgs e)
   {
  
     Ticket_MailTableAdapters.tbl_TicketTableAdapter tc;
     tc = new Ticket_MailTableAdapters.tbl_TicketTableAdapter();
     DataTable dt = new DataTable();
     dt = tc.GetEmail(dpl_cate.SelectedValue);
     foreach (DataRow row in dt.Rows)
      {
      string eml = (row["Emp_Email"].ToString());
      var fromAddress = "emailAddress";
      var toAddress = eml;
      const string fromPassword = "*****";
      string body = "Welcome..";
   // smtp settings
      var smtp = new System.Net.Mail.SmtpClient();
         {
           smtp.Host = "smtp.office365.com";
           smtp.Port = 587;
           smtp.EnableSsl = true;
  
           smtp.DeliveryMethod = System.Net.Mail.SmtpDeliveryMethod.Network;
           smtp.Credentials = new NetworkCredential(fromAddress, fromPassword);
           smtp.UseDefaultCredentials = false;
           smtp.Timeout = 600000;
         }
    // Passing values to smtp object
       smtp.Send(fromAddress, toAddress, subject, body);
       }
    } 
   }
  </code></pre>