Still, after how much time its been, I mean it cannot be more obvious.   If it came from WF, and Ramsay who is a Bolton now. It would have the official house Bolton seal, only way to confirm who its from. It has no seal, and pink wax writing. Every other Ramsay letter is written in blood. The pink wax is bolton wax yes, its obvious it is Maester Tybald writing it and Theon is dictating it with Stannis. Content wise......Jon Snow has no clue who the hell Reek is. So why would that