Add all to one message box and not individuals

Question

Hi,
This code loops through a datagrid and anything where the datedifference is above 7 days it sends them an email. But i want to display a message with all the recipients it has been sent to in one message box and not have to have it pop up individually for every different person.
Example
{ at the end of the sendmail function, if i put messagebox.show("Recipients" + emailAdd) It will display a message box for every recipient.
 
Thanks
How would i go about doing this?
 
private void sendMail(string emailAdd, string emailBod, string emailSub)
{
Outlook.Application oApp = new Outlook.Application();
Outlook.MailItem email = (Outlook.MailItem)(oApp.CreateItem(Outlook.OlItemType.olMailItem));
email.Recipients.Add(emailAdd);
email.Subject = emailSub;
email.Body = emailBod ;

((Outlook._MailItem)email).Send();

}
private void button1_Click(object sender, EventArgs e)
{
for (int i = 0; i < dataGridView1.Rows.Count; i++)
{
if (Convert.ToInt16(dataGridView1.Rows[i].Cells[7].Value) >= 7)
{
string cusCode = (dataGridView1.Rows[i].Cells[1].Value.ToString());
string letRef = (dataGridView1.Rows[i].Cells[0].Value.ToString());
string name = (dataGridView1.Rows[i].Cells[2].Value.ToString());
string emailAdd = (dataGridView1.Rows[i].Cells[5].Value.ToString());
string emailBod = ("Your Letter is " + dataGridView1.Rows[i].Cells[7].Value.ToString() + " days old" + "\r" + "\r" + "CustomerCode: " +
cusCode + "\r" + "Letter Reference: " + letRef + "\r" + "Full Name: " + name + "\r" + "\r" + "Regards " + System.Environment.UserName);
string emailSub = ("Your Letter(s) are " + dataGridView1.Rows[i].Cells[7].Value.ToString()) + " days old, Please see details below";
sendMail(emailAdd, emailBod, emailSub);