string FILENAME = Server.MapPath("~/GuestUserTemplate.txt");
    StreamReader objStreamReader = File.OpenText(FILENAME);
    string sEmailTemplate = "";
    string input = null;
    while ((input = objStreamReader.ReadLine()) != null)
    {
        sEmailTemplate = sEmailTemplate + input;
    }
    objStreamReader.Close();

    /* send an email */
    MailMessage msg = new MailMessage();
    msg.IsBodyHtml = true;
    msg.To.Add(new MailAddress(sToEmail));
    msg.From = new MailAddress(sFromEmail);
    msg.Subject = sEmailSubject;
    msg.Body = sEmailTemplate;
    //try
    {
        client.Send(msg);
    }
    //catch (Exception excm)
    {

    }

MIME-Version: 1.0
Content-Type: text/html; charset=us-ascii
Content-Transfer-Encoding: quoted-printable

Content-class: urn:content-classes:message
MIME-Version: 1.0
Content-Type: multipart/related;
    boundary="----_=_NextPart_001_01C9C98D.6552117E";
    type="multipart/alternative"

while ((input = objStreamReader.ReadLine()) != null)
{
    sEmailTemplate = sEmailTemplate + input;
}

sEmailTemplate = sEmailTemplate + objStreamReader.ReadToEnd();