What is the content-transfer encoding when sending emails via C # or is there no difference?

I am sending emails via C # below

MailMessage mail = new MailMessage();
mail.To.Add(txtTestEmail.Text);
mail.From = new MailAddress("noreply@monstermmorpg.com", "MonsterMMORPG");
mail.Subject = "Test email from MonsterMMORPG";
mail.Body = "This is test email sent from MonsterMMORPG";
mail.IsBodyHtml = true;
mail.SubjectEncoding = System.Text.Encoding.UTF8;
mail.BodyEncoding = System.Text.Encoding.UTF8;
SmtpClient smtp = new SmtpClient();
smtp.DeliveryMethod = SmtpDeliveryMethod.Network;
smtp.UseDefaultCredentials = true;
smtp.Host = "127.0.0.1";
smtp.Port = 25;
smtp.Send(mail);

      

        
        
        
      

    

The default is base64 I assume. But I am wondering which Content-Transfer-Encoding is best for sending email using a windows server 2008 r2 smtp server.

Is there any difference between different Content-Transfer-Encodings. Thank.