How much i understand you question is you are getting reply from wrong source as you want reply from the same email you specified above
string from = "noreplymail@gmail.com";
string to = "mail2@gmail.com";
string Password = "password123";
int port = Convert.ToInt32(ConfigurationManager.AppSettings["port"]);
string smtp = Convert.ToString(ConfigurationManager.AppSettings["smtp"]);
string Subject = "Enquiry";
string body = "Sender Name :" + txtname.Text + "\n" +
"Phone :" + txtphone.Text + "\n" +
"Email :" + txtemail.Text + "\n" +
"Address :" + txtaddress.Text + "\n"
+ "Enquiry :" + txtenquiry.Text;
string tor = txtemail.Text;
string reply = "Enquiry feedback";
string bbdy = "soon in touch";
MailMessage Msg = new MailMessage(from, to, Subject, body);
MailMessage replyMsg = new MailMessage(to, tor, reply, bbdy);