please try with MailMessage object and smtp.Send will not take 5 argument.
protected void ImgBtnSubmit_Click(object sender, ImageClickEventArgs e)
{
try
{
string toadd = "info@abc.co.uk";
var fromAddress = "info@abc.co.uk";
var toAddress = toadd;
const string fromPassword = "abc";
string subject = "Contact";
string bcc = "xyz@abc.co.uk";
string body = "<table border=1><tr><td> Name </td><td>" + txtname.Text + "</td></tr>" +
"<tr><td> Telephone </td><td> " + txttel.Text + "</td></tr>" +
"<tr><td> Mobile </td><td> " + txtmobile.Text + "</td></tr>" +
"<tr><td> Email </td><td> " + txtemail.Text + "</td></tr>" +
"<tr><td> Query </td><td> " + txtquery.Text + "</td></tr></table>";
var smtp = new System.Net.Mail.SmtpClient();
{
smtp.Host = "mail.abc.co.uk";
smtp.Port = 25;
smtp.EnableSsl = false;
smtp.DeliveryMethod = System.Net.Mail.SmtpDeliveryMethod.Network;
smtp.Credentials = new NetworkCredential(fromAddress, fromPassword);
smtp.Timeout = 20000;
}
MailMessage msg = new MailMessage();
msg.From = new MailAddress(fromAddress);
msg.To.Add(new MailAddress(toAddress));
msg.Bcc.Add(new MailAddress(bcc));
msg.Subject = subject;
msg.Body = body;
msg.IsBodyHtml = true;
smtp.Send(msg);
Response.Redirect("replycontact.aspx");
txtname.Text = "";
txttel.Text = "";
txtmobile.Text = "";
txtemail.Text = "";
txtquery.Text = "";
}
catch (Exception) { }
}