I have seen some fan post which was not quit as personal and charming as this one.

The letter seems genuine to us too, typed by a secretary but signed (quickly, in ballpoint) by Tolkien. For what it's worth, we've never seen a secretary-typed letter from Tolkien that he didn't sign personally, except for those clearly marked "p.p." (per procuriationem, by delegation to) with the secretary's name or initials. None of Tolkien's secretaries, as far as we know, ever tried to imitate his signature -- we doubt that he would have approved of the deception. Nor is it likely that Tolkien, who always took special care when writing to children, would not have signed this particular letter himself.

Wayne & Christina

When did Tolkien first get a secretary to answer his mail, I always thought it was 1965 which is the year after this letter?

The letter is from New Year's Eve 1964.
If he did now have a secretary at this time he would have written the letter himself. What is your feeling regarding style and content.
Did he write it himself? Does it tell anything about him?

When did Tolkien first get a secretary to answer his mail, I always thought it was 1965 which is the year after this letter?

You may be thinking of Joy Hill, who began to help Tolkien with his fan mail by mid-1965. Christopher Tolkien has assumed that his father obtained a secretary circa December 1957. The earliest mention we have seen of Tolkien having a secretary is in a letter to Rayner Unwin of 24 February 1959. (See our Chronology, pp. 799-800.)

Wayne & Christina