string v_smtpAddress ="smtp.xxx.com";//smtp地址，如smtp.163.com
     string v_sendMailUserName = "userName";//发送邮件使用的用户名
     string v_sendMailPassword = "userPwd";//发送邮件使用的密码
     string v_sendMailAddress ="phcis@163.com";//发送邮件的mail地址
     string v_receiveMailAddress ="phcis@163.com";//接收邮件的mail地址
     string v_mailSubject = "邮件主题";//邮件主题

     SmtpClient smtp = new SmtpClient(v_smtpAddress);
     smtp.Credentials = new System.Net.NetworkCredential(v_sendMailUserName, v_sendMailPassword);
     MailMessage mes = new MailMessage();

     mes.From = new MailAddress(v_sendMailAddress);
     mes.To.Add(v_receiveMailAddress);

     mes.Subject = v_mailSubject;
     mes.Body = TextArea1.Value;
     mes.IsBodyHtml = true;//使用是否html格式

      //增加附件
     System.Net.Mail.Attachment mailAttach_1 = new  Attachment(@"d:\b.txt");
     mes.Attachments.Add(mailAttach_1);
    
     smtp.Send(mes);
     mailAttach_1.Dispose();//释放由附件占用的资源