Send email problem when hosting

[blck]

Hi,

I rented a host. At localhost, i can control send email from this host to my email. However, when i hosting, it appears the below error:

The SMTP server requires a secure connection or the client was not authenticated. The server response was: host5.vdconline .vn ESMTP MailEnable Service, Version: 5.51-- denied access at 02/03/12 02:45:26

My code looks like:

if( dr != null)
            dr.Close();
        string mail = "select PassWord from UserTable where email = "+"'"+TextBox1.Text+"'";
        cmd = new SqlCommand(mail, conn);
        cmd.ExecuteNonQuery();
        dr = cmd.ExecuteReader();
        dr.Read();
        
        MailMessage msg = new MailMessage();
        SmtpClient smtp = new SmtpClient("*.*.*.*", 25);        
        msg.From = new MailAddress("*@*.*");        
        msg.To.Add(new MailAddress(TextBox1.Text));
        msg.Subject = "Recover password.";
        msg.Body = "Your password: " + dr[0].ToString();
        msg.IsBodyHtml = true;
                        
        smtp.EnableSsl = true;      
        smtp.UseDefaultCredentials = false;
        smtp.Credentials = new NetworkCredential("*@*.*", "******");  
        try
        {
            smtp.Send(msg);
            Label3.Text = "Email sent successfully";
        }
        catch (Exception ex)
        {
            Label3.Text = ""+ex.Message;
        }

Thanks in advance!