Dear …
Congratulations on your appointment as President to __(Name of Club/Chapter)__. We are very pleased that you have decided to accept this role. The appointment of President in this organization is not made lightly, as you know. This highest position of honor was offered to you in recognition of your overall services to __(Name of Organization)__, and to this __(Club/Chapter/etc.)__ in particular.
I know that I speak for all the members here when I say that we are fortunate to have someone of your caliber inducted into the position of President for __(Name of Club/Chapter)__. We are confident that you will carry out your new tasks with the same integrity and passion as you’ve shown throughout your membership in __(Name of Organization)__. Your leadership is welcomed by us all and I can safely say that you are assured of full cooperation from all the members of this __(Club/Chapter/etc.)__ during your term.
Again, on behalf of the members of the __(Name of Club/Chapter)__, congratulations on your appointment to President. We wish you a successful and rewarding term.
Yours very truly,