How to send mail using smtp in asp.net

Question

i need solution for this error 

At this point, I am running some error: Sending email failed. The SMTP server requires a secure connection, or the client failed authentication. Server response: 5.7.0. First you need to run the STARTTLS command. i1sm8651517pbj.70

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            // System.Web.Mail.SmtpMail.SmtpServer is obsolete in 2.0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("[e-mail]");
                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("[e-mail]")
                message.CC.Add("[e-mail]");
                message.CC.Add("[e-mail]");

                // You can specify Address directly as string
                message.Bcc.Add(new MailAddress("[e-mail]"));
                message.Bcc.Add(new MailAddress("[e-mail]"));

                //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.<br>" + ex.Message;
            }
        }
        #endregion

        #region "Reset"
        protected void btnReset_Click(object sender, EventArgs e)
        {
            txtName.Text = "";
            txtMessage.Text = "";
            txtEmail.Text = "";
        }
        #endregion
    }

Answer 1

You need to set the property SmtpClient.Credentials:

smtpClient.Credentials = new NetworkCredentials("yourUserName", "yourPassword");

This is what is used for authentication to send a message. You may also need to make sure SSL is enabled:

smtpClient.EnableSsl = true;

Property SMtpClient.Credentials MSDN Link

Answer 2

, GMail, SSL.
Google.

, web.config SSL :

<system.net>
    <mailSettings>
      <smtp deliveryMethod="network">
        <network host="smtp.gmail.com" port="587" enableSsl="true" userName="YOURUSERNAME" password="YOURPASSWORD" />
      </smtp>
    </mailSettings>
  </system.net>

:

smtpClient.EnableSsl = true;

Answer 3

you can check my message on how to send an email using gmail authentication

send an email with gmail smtp server

Answer 4

I think you forgot to set the property EnableSSLto truewhich is required for gmail.

Here is a sample code:

protected void btnSend_Click(object sender, EventArgs e)
{
    try
    {              
        MailMessage msg = new MailMessage();
        msg.From = new MailAddress(txtFrom.Text);                
        msg.To.Add(new MailAddress(txtTo.Text));
        msg.Subject = txtSubject.Text;
        msg.Body = txtBody.Text;                           

        SmtpClient mySmtpClient = new SmtpClient();
        System.Net.NetworkCredential myCredential = new System.Net.NetworkCredential(txtFrom.Text,txtPwd.Text);
        mySmtpClient.Host = "smtp.gmail.com";
        mySmtpClient.Port=587;
        mySmtpClient.EnableSsl = true;
        mySmtpClient.UseDefaultCredentials = false;
        mySmtpClient.Credentials = myCredential;                

        mySmtpClient.Send(msg);
        msg.Dispose();
        lberr.Text="Message sent successfully";
        clrtxt();
    }
    catch(SmtpException)
    {
        lberr.Text="SMTP Error handled";
    }
}

Answer 5

public void SendMail()
{
    System.Net.Mail.MailMessage mail = new System.Net.Mail.MailMessage();
    mail.To.Add(MailTo.Text);
    mail.From = new MailAddress(MailFrom.Text,"Invoice");
    mail.Subject = Subject.Text;
    mail.Body = Body.Text;
    mail.IsBodyHtml = true;



    string FileName = Path.GetFileName(FileUploadAttachments.PostedFile.FileName);
    Attachment attachment = new Attachment(FileUploadAttachments.PostedFile.InputStream ,FileName);
    mail.Attachments.Add(attachment);            

    SmtpClient client = new SmtpClient();
    client.Credentials = new System.Net.NetworkCredential("[e-mail]", "Your_Email_Password");
    client.Host = "smtpout.secureserver.net";
    client.Port = 80;
    try
    {
        client.Send(mail);
    }
    catch (Exception ex)
    {
        System.Windows.Forms.MessageBox.Show(ex.Message);
    }
}