Hot to Send mail and reply mail in Asp.net

using System.Net.Mail;
using System.Text;

 public string SendFromMail, SendToMail, Body, subject;
public void SendMail(string SendToMail, string SendFromMail, string subject, string Body)
    {
        try
        {
            MailAddress SendFrom = new MailAddress(SendFromMail);
            MailAddress SendTo = new MailAddress(SendToMail);
            MailMessage MyMessage = new MailMessage(SendFrom, SendTo);

       
            MyMessage.Subject = subject;
            MyMessage.Body = Body;
            MyMessage.IsBodyHtml = true;
            string mSMTPServer = "smtpout.secureserver.net";// ConfigurationSettings.AppSettings["smtpServer"].ToString();
            SmtpClient SmtpMail = new SmtpClient(mSMTPServer);
            System.Net.NetworkCredential SMTPUserInfo = new System.Net.NetworkCredential("hr@companyname.com ", "Password");//that mail where i send the mail
            SmtpMail.UseDefaultCredentials = false;
            SmtpMail.Credentials = SMTPUserInfo;
            SmtpMail.Send(MyMessage);
        }
        catch (Exception ex)
        {
            ex.ToString();
        }
    }

    void SendMailToUser()
    {
        SendFromMail = "hr@companyname.com";
        SendToMail = "hr@companyname.com";
     
     
        subject = "Enquiry";
        Body += "Dear Support," + "<br /><br />There was an enquiry from companyname.com. Following are the details:";
        Body += "<br /><br /> Name:&nbsp;&nbsp;" + txtfullname.Text;
        Body += "<br />Email Id:&nbsp;&nbsp;" + txtemailAddress.Text;
        Body += "<br />Mobile No:&nbsp;&nbsp;" + txtMobileno.Text;
        Body += "<br />Address:&nbsp;&nbsp;" + txtAddress.Text;
        Body += "<br />City:&nbsp;&nbsp;" + txtcity.Text;
        Body += "<br />Message:&nbsp;&nbsp;" + txttotalexperience.Text;
        Body += "<br /><br /><br />Regards";
        Body += "<br />System Admin";
        Body += "<br />companyname.com";

        //Body += "Name: <br /><br />Please use the following key to register your app upon the first run of the application:<br /><br /><div align=\"center\">";

        SendMail(SendFromMail, SendToMail, subject, Body);

    }

    void SetTheReplyToHeader()
    {
        StringBuilder builder = new StringBuilder();
        builder.Append("Dear");
        builder.Append(" ");
        builder.Append(txtfullname.Text).AppendLine().AppendLine();
        builder.Append("Thanks for your query. A HR executive will shortly contact you soon.").AppendLine().AppendLine();
        builder.Append("Regards").AppendLine();
        builder.Append("Support Team").AppendLine();
        builder.Append("xxxxxxxxxxxxxx").AppendLine();
        builder.Append("xxxxxxxxxxxxxx
        builder.Append("xxxxxxxxxxx
        builder.Append("xxxxxxxxxxxxxxxxx).AppendLine();

        MailMessage mail = new MailMessage();
        SmtpClient SmtpServers = new SmtpClient("smtpout.secureserver.net"); //Mail Server Name
        mail.From = new MailAddress("hr@companyname.us");
        mail.To.Add(txtemailAddress.Text);//Who save the data
        mail.Subject = "companyname";
        mail.Body += builder.ToString();
        SmtpServers.Port = 25;
        SmtpServers.UseDefaultCredentials = true;
        SmtpServers.Credentials = new System.Net.NetworkCredential("hr@companyname.com ", "Password");
        SmtpServers.Send(mail);
    }