Dear John,
    I've just read in the company newsletter that you've retiring next week and going back to California, and I'm writing to congratulate you upon your well-deserved retirement.
    I'm sure you'll be missed by everyone, not only for the high degree of competence with which you handled your job, but also because you were a very good friend to a lot of people. Your thirty years of experience has made you an invaluable employee, and it will be extremely difficult to replace you.
    I sincerely hope you'll enjoy your new life in California. The dry climate there, I believe, will do your health a world of good. Please try to keep in touch, as we would love to hear how you've settling down to California life! Good luck for the future and I look forward to hearing from you now and again.
    All my best wishes,
    Jack Chen