GemBox Word Document to Email ,£ character is converted to question mark

Question

GemBox Word Document to Email, convert £ character to question mark for one of my clients.

my code I same as on gembox site.

GemBox.Document.ComponentInfo.SetLicense(this.GemBoxDocumentLisense);
 GemBox.Email.ComponentInfo.SetLicense(this.GemBoxEmailLisense);

 var document = DocumentModel.Load(documentPath);
 using (MemoryStream gemBoxOutput = new MemoryStream())
 {
document.Save(gemBoxOutput , new GemBox.Document.HtmlSaveOptions()
{
    HtmlType = GemBox.Document.HtmlType.Mhtml,
    UseContentIdHeaders = true,
  //Encoding = Encoding = Encoding.UTF8
});
MailMessage.Load(gemBoxOutput, MailMessageFormat.Mhtml);

I want to set utf-8 encoding using gembox without destroying template.I tried to set the encoding in htmlsaveoptions but it destroy the template and the email is not properly loaded in outlook.