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

　　This promotion¹ 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.