how to send mail from win form

Question

 error:

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

below my code 

 

 

 

 

private void button1_Click(object sender, EventArgs e)

{

try

{

SmtpClient client = new SmtpClient("smtp.gmail.com");

client.Port = 587;

client.EnableSsl = true;

client.Timeout = 100000;

client.DeliveryMethod = SmtpDeliveryMethod.Network;

client.UseDefaultCredentials = false;

client.Credentials = new NetworkCredential(

"[email protected]", "durga12345678");

MailMessage msg = new MailMessage();

msg.To.Add(textBox1.Text);

msg.From = new MailAddress("[email protected]");

msg.Subject = textBox2.Text;

msg.Body = textBox4.Text;

Attachment data = new Attachment(textBox3.Text);

msg.Attachments.Add(data);

client.Send(msg);

MessageBox.Show("Successfully Sent Message.");

}

catch (Exception ex)

{

MessageBox.Show(ex.Message);

}

}

private void button2_Click(object sender, EventArgs e)

{

OpenFileDialog dlg = new OpenFileDialog();

if (dlg.ShowDialog() == DialogResult.OK)

{

textBox3.Text = dlg.FileName.ToString();

}

}