not able to send mail with attachment to multiple reciepent

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C#

I am trying to send mail with attachment to multiple reciepent but manage to send only text message not attachment
fatching email address from excel file
Here is my code

using System;
using System.Collections;
using System.Configuration;
using System.Data;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Net;
using System.Net.Security;
using System.Net.Mail;
using System.IO;

public partial class _Default : System.Web.UI.Page
{
    DataTable dt = new DataTable();
    Excel ex = new Excel();
    String sql;
    DataSet ds = new DataSet();

    protected void Page_Load(object sender, EventArgs e)
    {

    }
    protected void btnupload_Click(object sender, EventArgs e)
    {
        if (FileUpload1.HasFile)
        {
            bool uplod = true;
            string fleUpload = Path.GetExtension(FileUpload1.FileName.ToString());
            if (fleUpload.Trim().ToLower() == ".xls" |
        fleUpload.Trim().ToLower() == ".xlsx")
            {
                // Save excel file into Server sub dir
                // to catch excel file downloading permission
                FileUpload1.SaveAs(Server.MapPath("~/email/" +
                   FileUpload1.FileName.ToString()));
                string uploadedFile = (Server.MapPath("~/email/" +
                    FileUpload1.FileName.ToString()));
                try
                {
                    //dt = xlsInsert(uploadedFile);
                    //GridView1.DataSource = dt;
                    //GridView1.DataBind();
                }
                catch (Exception)
                {
                    uplod = false;
                    this.lblmessage.Text = "System uploading Error";
                }
                //File.Delete(uploadedFile); // Delete upload Excel
                //file in sub dir 'lsUploadFile' no need to keep...
            }
            if (uplod)
                    {
                string mess1 = "File has successfully uploaded.";
                this.lblmessage.Text = mess1;
            }
        }
        else
        {
            this.lblmessage.Text = "Please select file to upload !";
        }
    }
    protected void send_Click(object sender, EventArgs e)
    {
        ds.Clear();
        sql = "select email from [Sheet1$]";
        ds = ex.select(sql);
        for (int i = 0; i < ds.Tables[0].Rows.Count; i++)
        {
            int flag=0;
            if (ds.Tables[0].Rows[i]["email"].ToString() == "")
            {
                flag = 1;
                break;
            }

            #region Email
            MailMessage mail = new MailMessage();
            mail.To.Add(ds.Tables[0].Rows[i]["email"].ToString());
            mail.From = new MailAddress("deanpg@pacific-university.ac.in");
            mail.Subject =subject.Text.ToUpper();

            mail.Body = "<table width="100%><tr"><td width="40%>1."> Message  </td>" + "<td width="60%>"" mode="hold" />
            if (FileUpload2.HasFile)
            {
                mail.Attachments.Add(new Attachment(FileUpload2.PostedFile.InputStream, FileUpload2.FileName));
            }
            mail.IsBodyHtml = true;
            SmtpClient client = new SmtpClient();
            client.DeliveryMethod = SmtpDeliveryMethod.Network;
            client.EnableSsl = true;
            client.Host = "smtp.gmail.com";
            client.Port = 587;
            client.Credentials =
                new System.Net.NetworkCredential("deanpg@pacific-university.ac.in", "pacific@phd");

            try
            {
                client.Send(mail);
                lblthen.Text = "Message has been sent succcessfully.";
            }
            catch (Exception ext)
            {
                lblmess.Text = ext.Message;
            }

            #endregion
        }
    }
}