(The owl finds Harry despite the protection charms that are hiding his camp.)
Harry,
I hope you'll forgive the brevity of this message, as I am cold and rushed and at the moment I'm fairly certain you're feeling the same. If it eases the cold at all for you, I do believe that the decision to have you leave Hogwarts was the right one. The school has been less a target than it might have been.
However, there are things that must be seen to, and we have perhaps moved too slowly to see them through.
To the matters for which you are now searching; you already know the fate of the ring of Marvolo Gaunt and the diary of his unfortunate grandson.
From what you have told me of the locket, which I hope you now have possession of, I believe it is rightly identified as belonging to Salazar Slytherin. I believe the answer to the riddles of the final horcrux lie in the other Hogwarts Founders, though I know that Miss Granger has likely already come to this same conclusion. Unfortunately, Harry, I believe that there are two more to be found, and none of my months of searching has yielded anything more than the idea that one of the remaining items must reside at Hogwarts itself.
I have, for lack of better idea, been a foolish old man, ignoring my duties for a search that is not entirely my own, and perhaps allowing things to linger too long for that. The travels that I am on now perhaps hold more answers to our Riddles, Mr Potter. I do wish that I had one more chance to take tea with you and discuss this all, but I fear my journey will be too long for that.