code: public static void sendAttachmentFile(final byte[] content, final String mimeType) {
  		dispatchConversationTask(new ConversationDispatchTask() {
  			@Override
  			protected boolean execute(Conversation conversation) {
  				ByteArrayInputStream is = null;
  				try {
  					is = new ByteArrayInputStream(content);
  					sendAttachmentFile(is, mimeType);
  				} finally {
  					Util.ensureClosed(is);
  				}
  				return true;
  			}
  		}, "send attachment file");
  	}
docs: Sends a file to the server. This file will be visible in the conversation view on the server, but will not be shown
  in the client's Message Center. A local copy of this file will be made until the message is transmitted, at which
  point the temporary file will be deleted.
  
  @param content  A byte array of the file contents.
  @param mimeType The mime type of the file.