Unable to send the Data in the Document to all Mail Ids at a time

<tr>

<td><asp:Label id="lbloracle11gDBA" runat="server" Text="Oracle 11g DBA"></asp:Label></td>
<td><asp:TextBox ID="txtoraclebatchid" runat="server" 
     ontextchanged="txtoraclebatchid_TextChanged" AutoPostBack="true"></asp:TextBox></td>
<td><asp:TextBox ID="txtoraclestdt" runat="server" ></asp:TextBox></td>
<td><asp:TextBox ID="txtoracleendt" runat="server" ></asp:TextBox></td>
<td><asp:TextBox ID="txtoracletimings" runat="server" ></asp:TextBox></td>
<td><asp:FileUpload ID="upload" runat="server" /></td>
<td><asp:Button ID="btnoraclesend" runat="server" Text="Send"                 onclick="btnoraclesend_Click" /></td>

</tr>

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.Data.SqlClient;
using System.Net.Mail;


public partial class _Default : System.Web.UI.Page 
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }

    
    protected void btnoraclesend_Click(object sender, EventArgs e)
    {


        SqlConnection conn = new SqlConnection();
        conn.ConnectionString = "Data Source=xxxxx; User Id=xxxxx; Password=xxxxxx; Initial Catalog=xxxxxxx; Integrated Security=SSPI;";
        conn.Open();


        SqlCommand cmd = new SqlCommand();
        cmd.Connection = conn;
        cmd.CommandText = "select EMail_1 from Student_Info where Branch_Code='ap' and Student_ID in(select Student_ID from Admissions where Branch_Code='ap' and Batch_ID='" + txtoraclebatchid.Text + "')";
        cmd.CommandType = CommandType.Text;

        SqlDataAdapter da = new SqlDataAdapter(cmd);
        da.SelectCommand = cmd;
        DataSet ds = new DataSet();
        da.Fill(ds);
             

        if (ds.Tables[0].Rows[0][0] != null)
        {
            int count = ds.Tables[0].Rows.Count;

            for (int i = 0; i < count; i++)
            {
                
                MailMessage mm = new MailMessage();
                mm.To.Add(ds.Tables[0].Rows[i][0].ToString());
                mm.From = new MailAddress("xxxxxxxxxx");
                mm.Subject = "Asp.net Test Email";
                                
               
           if (upload.HasFile)
          {
              mm.Attachments.Add(new Attachment(upload.PostedFile.InputStream, upload.FileName));
          }
                      
                
                mm.Body = "Hello world";
                SmtpClient s = new SmtpClient("smtp.xxxxxxxxx.com");
                s.Send(mm);
                Response.Write("Email Sent");

            }
            
        }
                
        conn.Close();
        

    }
}