How to put line break in Mail body using C# in ASP.Net

When I write more than one paragraph in the mail body, it is going only as a single paragraph. There is no space between paragraph. For example in the mail paragraph the body is like that :

I am coming tomorrow. I will call you when I landed. fdfdfffdfdfdffd

fddffdfff.

See you soon.

Fatih

the result like that:

I am coming tomorrow. I will call you when I landed. fdfdfffdfdfdffd

fddffdfff. See you soon. Fatih

How can we solve this problem?

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
using System.Data.OleDb;
using System.Net.Mail;
using System.Net;
using System.Drawing;

public partial class _Default : System.Web.UI.Page
{
   protected void Page_Load(object sender, EventArgs e)
    {
        if (Session["nick"] == null)
            Response.Redirect("giris.aspx");
        else
            Response.Write(""); ;
    }

    protected void Button1_Click(object sender, EventArgs e)
    {
        string isim = string.Empty;
        string soyisim = string.Empty;
        string email = string.Empty;
        string body = string.Empty;
        OleDbConnection cnn = new OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + Server.MapPath(@"..\datam_benim2541\uyelerim_benim2541.mdb"));
        OleDbCommand bulten = new OleDbCommand("SELECT isim, soyisim, email FROM uyeler", cnn);
        if (cnn.State == ConnectionState.Closed)
        {
            cnn.Open();
        }
        OleDbDataAdapter bdr = new OleDbDataAdapter(bulten);
        DataTable dt = new DataTable();
        bdr.Fill(dt);
        cnn.Close();

        foreach (DataRow row in dt.Rows)
        {
            isim = row["isim"].ToString();
            soyisim = row["soyisim"].ToString();
            email = row["email"].ToString();
            body = string.Format("Sayın; {0} {1},<br/><br/>{2}<br/><br/>", isim, soyisim, txtmesaj.Text, "\r\n");
            SendEmail(email, txtkonu.Text, body);
            }

        lblmesaj.ForeColor = System.Drawing.Color.Green;
        lblmesaj.Text = "E-Postalar Başarıyla Gönderildi";

        txtkonu.Text = "";
        txtmesaj.Text = "";
    }

    private bool SendEmail(string recipient, string subject, string body)
    {
        MailMessage mm = new MailMessage("xxxx@xxxx.com.tr", recipient);
        mm.Subject = subject;
        mm.Body = body;
        mm.IsBodyHtml = true;
        SmtpClient smtp = new SmtpClient();
        smtp.Host = "mail.xxxx.com.tr";
        smtp.EnableSsl = false;
        NetworkCredential NetworkCred = new NetworkCredential();
        NetworkCred.UserName = "xxxx@xxxx.com.tr";
        NetworkCred.Password = "xxxxx";
        smtp.UseDefaultCredentials = true;
        smtp.Credentials = NetworkCred;
        smtp.Port = 587;
        smtp.Send(mm);
        return true;
    }
    protected void LinkButton1_Click1(object sender, EventArgs e)
    {
        Session.Abandon();
        Response.Redirect("giris.aspx");
    }
}