Question

here is the code.

void sendMail()
{
    MailMessage mail = new MailMessage();

    mail.To.Add("[e-mail]");
    mail.From = new MailAddress("[e-mail]", txt_name.Text);
    mail.Subject = txt_subject.Text;
    mail.Body = txt_body.Text;

    SmtpClient smtp = new SmtpClient("smtp.gmail.com");
    smtp.EnableSsl = true;

    NetworkCredential yetki = new NetworkCredential("[e-mail]", "11111111");
    smtp.Credentials = yetki;

    smtp.Send(mail);

    Response.Write("mailiniz başarılı bir şekilde gönderilmiştir");
}

protected void btn_gonder_Click(object sender, EventArgs e)
{
    sendMail();
}

Answer 1

The error indicating it is unhandled means you didn’t catch the exception. Now what you actually do in the catch block to handle the exception is up to you, such as logging it to a file, queuing a retry, or showing a message box. Or trying to do something to prevent the exception in the first place.

protected void btn_gonder_Click(object sender, EventArgs e)
{
  try{
    sendMail();
  }
  catch(Exception ex)
  {

  }
}

Also note you can access ex.Message to see the exception message, or add a break point to the catch block and inspect ex. It is possible there is more you need to do to get it to work with gmail because of the requirements for authentication. I don’t know if the network credentials are enough. I’ve always had trouble with it and resorted to using my ISP’s email account that doens’t require authentication.