Problem while sending mail

Question

Hello Guys,

 

i am having problem while writing codes to implement mail messeging in asp .net with c#

 

i am using following code 

 

try{

using (MailMessage mm = new MailMessage(txtEmail.Text, txtTo.Text))

{

mm.Subject = txtSubject.Text;

mm.Body = txtBody.Text;

if (fuAttachment.HasFile)

{

string FileName = Path.GetFileName(fuAttachment.PostedFile.FileName);

mm.Attachments.Add(new Attachment(fuAttachment.PostedFile.InputStream, FileName));

}

mm.IsBodyHtml = false;

SmtpClient smtp = new SmtpClient();

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

smtp.EnableSsl = true;

NetworkCredential NetworkCred = new NetworkCredential(txtEmail.Text, txtPassword.Text);

smtp.UseDefaultCredentials = true;

smtp.Credentials = NetworkCred;

smtp.Port = 587;

smtp.Send(mm);

ClientScript.RegisterStartupScript(GetType(), "alert", "alert('Email sent.');", true);

}

}

catch(Exception ex)

{

Response.Write("<script>alert("+ex.Message+")</script>");

}

 

 

 

The error i am facing is

 

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. ra13sm19230672pac.29 - gsmtp