C# Attachment File & MailMessage Arabic character

I have an issue when sending an attachment file that contains Arabic characters which appear as ???? for file name. However, this issue not appear if the file name is English. I tried to use UTF-8 fro encoding but not work.

    private static void GenerateAndSendMail(string subject, string body, List<string> filesFullPath = null)
    {
        try
        {
            var mailMessage = new MailMessage();
            mailMessage.From = new MailAddress(MyAppConfigService.CurrentUser.Email);
            mailMessage.Subject = subject;
            mailMessage.IsBodyHtml = true;
            mailMessage.Body = body;
            mailMessage.SubjectEncoding = Encoding.Unicode;
            mailMessage.HeadersEncoding = Encoding.Unicode;
            mailMessage.BodyEncoding = Encoding.Unicode;

            if (filesFullPath != null && filesFullPath.Count > 0)
            {
                foreach (var item in filesFullPath)
                {
                    var Attachment = new Attachment(item);
                    Attachment.NameEncoding = Encoding.Unicode;
                    mailMessage.Attachments.Add(Attachment);
                }
            }
            //save the MailMessage to the filesystem
            var filename = Path.GetTempPath() + "mymessage.eml";
            mailMessage.Save(filename);
            //Open the file with the default associated application registered on the local machine
            Process.Start(filename);
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }