Arabic format of CSV file show in computer but not in mobile

Question

I make production report then send by email automatically by timer

but problem Arabic language not show in mobile iPhone 5 or iPhone 4

although when i open the file sending by email  from any computer it is open and show Arabic format good

but from mobile it not show Arabic format AND it show it in understood characters and symbol's why 

this is my code as below

                    

StreamWriter sw = new StreamWriter("I:\\SalesData" + DateTime.Today.AddDays(-1).ToString("dd-MM-yyyy") + ".csv", false, System.Text.Encoding.Default);

for (int i = 0; i < dataGridView1.Columns.Count; i++)
{
sw.Write(dataGridView1.Columns[i].HeaderText);
if (i != dataGridView1.Columns.Count)
{
sw.Write(",");
}
}
sw.Write(sw.NewLine);
foreach (DataGridViewRow dr in dataGridView1.Rows)
{
for (int i = 0; i < dataGridView1.Columns.Count; i++)
{
sw.Write(dr.Cells[i].Value);
if (i != dataGridView1.Columns.Count)
{
sw.Write(",");
}
}
sw.Write(sw.NewLine);
}
sw.Flush();
sw.Close();
string smtpAddress = "smtp.gmail.com";
int portNumber = 587;
bool enableSSL = true;
string emailFrom = "[email protected]";
string password = "pass12";
string emailTo = "[email protected]";
string subject = "Order Date" + label31.Text + "Finish" + "(" + label39.Text + ")";
string body = "Summary for Date" + "" + label31.Text + "" +
"Quantity Required" + "" + "(" + label2.Text + ")" + "/" +
"Quantity Shipped" + "/" + "(" + label3.Text + ")" + "/" +
"Quantity Remaining" + "/" + "(" + label4.Text + ")";
using (MailMessage mail = new MailMessage())
{
mail.From = new MailAddress(emailFrom);
mail.To.Add(emailTo);
mail.Subject = subject;
mail.Body = body;
mail.IsBodyHtml = true;
mail.Attachments.Add(new Attachment("I:\\SalesData" + DateTime.Today.AddDays(-1).ToString("dd-MM-yyyy") + ".csv"));
System.Net.Mail.SmtpClient smtp = new SmtpClient(smtpAddress, portNumber);
smtp.UseDefaultCredentials = false;
smtp.DeliveryMethod = SmtpDeliveryMethod.Network;
smtp.Credentials = new NetworkCredential(emailFrom, password);
smtp.EnableSsl = enableSSL;
smtp.Send(mail);
}
}
How i change my code to accept Arabic language in email in mobile and computer

In computer Arabic language display OK without problem

but in mobile Arabic language not show and strange character's show