EncodingEmailDocument.cs

 // Setup GroupDocs.Viewer config
ViewerConfig config = Utilities.GetConfigurations();
 
 //Initialize viewer handler
ViewerImageHandler viewerImageHandler = new ViewerImageHandler(viewerConfig);
  
 //Set encoding
Encoding encoding = Encoding.GetEncoding("shift-jis");
 
  //Set image options
ImageOptions imageOptions = new ImageOptions();
imageOptions.EmailOptions.Encoding = encoding;
  
//Get email document pages with encoding
string emailDocumentGuid = "document.msg";
List<PageImage> emailDocumentPages = viewerImageHandler.GetPages(emailDocumentGuid, imageOptions);
  
 //Get email document info with encoding
DocumentInfoOptions emailDocumentInfoOptions = new DocumentInfoOptions(emailDocumentGuid);
emailDocumentInfoOptions.EmailDocumentInfoOptions.Encoding = encoding;
DocumentInfoContainer emailDocumentInfoContainer = viewerImageHandler.GetDocumentInfo(emailDocumentInfoOptions);