sending mail from gmail

Question

 Hii,

i am facing the following error while sending the mail following is my code please help 

 

“The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.5.1 Authentication Required.

 

thanks in advance 

 

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protected void btnSubmit_Click(object sender, EventArgs e)

{

try

{

MailMessage Msg = new MailMessage();

// Sender e-mail address.

Msg.From = new MailAddress(txtUsername.Text);

// Recipient e-mail address.

Msg.To.Add(txtTo.Text);

Msg.Subject = txtSubject.Text;

Msg.Body = txtBody.Text;

// your remote SMTP server IP.

SmtpClient smtp = new SmtpClient();

smtp.Host = "smtp.gmail.com";

smtp.Port = 587;

smtp.Credentials=new System.Net.NetworkCredential(txtUsername.Text,txtpwd.Text);

smtp.EnableSsl = true;

smtp.Send(Msg);

Msg = null;

Page.RegisterStartupScript("UserMsg", "<script>alert('Mail sent thank you...');if(alert){ window.location='SendMail.aspx';}</script>");

}

catch (Exception ex)

{

Console.WriteLine("{0} Exception caught.", ex);

}

}

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