SMTP mail sending through ASP.Net

I have a problem regarding smtp mail sending with asp.net.When I attempt to send through the smtp protocol,I get the following error.

The server response was: 5.5.1 Authentication Required 

I'm using something like this;

  string mess = "";

    mess += "<b>You have mail</b></br>";
    mess += "<b>Name Surname</b>" + textName.Text + "</br>";
    mess += "<b>Email adress</b>" + textEmail.Text + "</br>";
    mess += "<b>Subject</b>" + textSubject.Text + "</br>";
    mess += "<b>Message</b>" + textMessage.Text + "</br>";
    mess += "<b>Date</b>" + DateTime.Now.ToString();



    MailMessage msg = new MailMessage();
    msg.IsBodyHtml = true;
    msg.To.Add("oruc_esma@hotmail.com");
    msg.From = new MailAddress("turkishcorpus1@gmail.com", "Esma oruc",System.Text.Encoding.UTF8);
    msg.Subject = textSubject.Text;
    msg.Body =  mess;

    SmtpClient smp = new SmtpClient();
    smp.Credentials = new NetworkCredential("turkishcorpus1@gmail.com", "my password");
    smp.Port = 587;
    smp.Host = "smtp.gmail.com";
    smp.EnableSsl = true;


    smp.Send(msg开发者_StackOverflow中文版);
} 

Thanks in advance,

For sending gmail through SMTP in ASP.NET, use this

var smtp = new SmtpClient
           {
               Host = "smtp.gmail.com",
               Port = 587,
               EnableSsl = true,
               DeliveryMethod = SmtpDeliveryMethod.Network,
               UseDefaultCredentials = false,
               Credentials = new NetworkCredential("turkishcorpus1@gmail.com", "my password")
           };
using (var message = new MailMessage("turkishcorpus1@gmail.com", "oruc_esma@hotmail.com")
                     {
                         Subject = "This is the title of the mail",
                         Body = "This is the body"
                         //,IsBodyHtml = true //optional
                     })
{
    smtp.Send(message);
}