Strange characters title when post to Blogspot via Email

Question

When i post to blogspot via email by SMTPServer.Send(MyMailMessage), the title of post have some strange characters like that b���n (bạn).

Image for detail

They are Vietnamese. The content is ok. Just title of post get this problem. When i post by regular sending email in Webbrowser everything is right. This is my code (VB.NET)

MyMailMessage.To.Add(ToEmail)
MyMailMessage.Subject = TieuDe.Trim
MyMailMessage.SubjectEncoding = System.Text.Encoding.UTF8
MyMailMessage.Body = NoiDung 
SMTPServer.Send(MyMailMessage)

Please help me. Thanks.