How to authenticate SMTP credentials

Hi all I have a code that send email, now what I want to do is to check the provided credential if it is valid or not. please refer on my code below.                 SmtpClient Client = new SmtpClient("Myhost.com", 25);                 Client.EnableSsl = false;                 Client.UseDefaultCredentials = false;                 Client.Credentials = new NetworkCredential("myUserName", "MyPass");                                 Client.DeliveryMethod = SmtpDeliver ...