1)
dear xxx
it was with great pleasure that i read of your promotion to the position of (position) with (name of firm)
i am sure your firm has made a very wise choice and that you will excel in your new role as (position)
please accept my congratulation on your promotion and my very best wishes for your continuing success.
2)
dear xxx
congratulations on your recent promotion to (position)
i know how hard you have worked to earn the recognition you presently enjoy at (name of firm) , and i feel that they are very wise in having made their choice.
please accept our best wishes for your success in your new position.
3)
agai, congratulations and best wishes for continued success.
because of our close association with you over the past ten years, we know how well you are qualified for this important office. you earned the promotion through years of hard work and we are delighted to see your true ability win recognition.