If create the body property as
System.Net.Mail.MailMessage message = new System.Net.Mail.MailMessage(); message.Body =\"First Line \\n second line\";
Try this
IsBodyHtml = false, BodyEncoding = Encoding.UTF8, BodyTransferEncoding = System.Net.Mime.TransferEncoding.EightBit
If you wish to stick to using \r\n
I managed to get mine working after trying for one whole day!