email html form data in text file

System.Text.StringBuilder obj=new System.Text.StringBuilder();
obj.Append("<table><tr><td>");
obj.Append("Dear "+dr["Name"].ToString()); 
Please use the required fields in the above mentioned ways. Then initialise the obj in a string variable as shown below.
obj.Append("</td></tr></table>");
string body=obj.ToString(); 
Now U can send this body in mail. For sending mail, there r lots of link available. U can have a look on the following link also.

FileStream fileStream = new FileStream(@"E:\file.txt", FileMode.OpenOrCreate);

StreamWriter streamWriter = new StreamWriter(fileStream);

streamWriter.BaseStream.Seek(0, SeekOrigin.End);
streamWriter.Write(" File Write Operation Starts : ");
streamWriter.Flush();
streamWriter.Close();