如何发送电子邮件与附件的文件没有扩展

我创建了c#控制台应用程序，我不能发送文件附件名为"testfile"的电子邮件，没有扩展名。

它成功发送，但只有第一个附件("test.png")我怎样发送这个文件?

下面是我的代码:

internal static void SendTest()
{
    MailMessage mail = new MailMessage("Punter@gmail.com", "Michael378@live.com",
                                       "Success", "Attachment email");
    SmtpClient SmtpServer = new SmtpClient("smtp.gmail.com", 587);
    SmtpServer.Credentials = new System.Net.NetworkCredential("Punter@gmail.com",      "BrudoTass");
        SmtpServer.EnableSsl = true;
        string test1 = @"C:'Users'Admin'Desktop'test.png";          //Picture
        string test2 = @"C:'Users'Admin'Desktop'testfile";   //File without extension
        var attachment1 = new Attachment(test1);
        var attachment2 = new Attachment(test2);
        mail.Attachments.Add(attachment1);
        mail.Attachments.Add(attachment2);
        SmtpServer.Send(mail);
    }

        foreach (MessageAttachment ma in msg.Attachments)
        mail.Attachments.Add(BuildAttachment(ma));
        private Attachment BuildAttachment(MessageAttachment ma)
        {
            Attachment att = null;
            if (ma == null || ma.FileContent == null)
                    return att;
            att = new Attachment(new MemoryStream(ma.FileContent), ma.FileName + ma.FileType, ma.FileType.GetMimeType());
            att.ContentDisposition.CreationDate = ma.CreationDate;
            att.ContentDisposition.ModificationDate = ma.ModificationDate;
            att.ContentDisposition.ReadDate = ma.ReadDate;
            att.ContentDisposition.FileName = ma.FileName;
            att.ContentDisposition.Size = ma.FileSize;
            return att;
        }