It is our great pleasure to inform you that you have been promoted to the challenging and demanding position of [position]

　　This promotion is in recognition of the fine work you have done for this firm.  We are very confident that you will meet the new responsibilities which accompany the position of   [position]  with the same level of enthusiasm and enterprise which you have exhibited since you came to work with our firm.

　　Please accept our congratulations on your new promotion.