Send mail in c#

// using this code in send mail button Onclick event

string username = //your name
                string answer = null;
                string mail = null;
               
              
                    MailMessage msg = new MailMessage();
                    msg.From = new MailAddress("...."); //from mail id
                    msg.To.Add(".."); //to mail id
                    msg.Subject = "sample test";
                    msg.Body = "UserName:" + username + ";
                    SmtpClient smtp = new SmtpClient("smtp.gmail.com");
                    smtp.EnableSsl = true;
                    smtp.Port = 25; // your smtp port number here 
                   System.Net.NetworkCredential SMTPUserInfo = new System.Net.NetworkCredential("//user mail id", "//user password");

                    try
                    {
                        smtp.UseDefaultCredentials = false;
                        smtp.Credentials = SMTPUserInfo;
                        smtp.Send(msg);
                        ScriptManager.RegisterStartupScript(this.Page, this.GetType(), "Alert", "alert('Your Password has been sent to your Email id')", true);
                    }
                    catch (Exception exe)
                    {
                        Response.Write(exe.Message.ToString());
                    }