Regarding Commuication Thru' E-mail

Hello All,
Recently there was a mail communication sent out by our MD regarding change in roles and responsibilities of one of our Senior Manager and he being replaced as the Group Head for one of our verticals.
There was no official letter issued to the employee regarding change in his designation.
My query is will this mail communication hold good for the changes made in Organization or should I issue an official letter to the employee about change in his designation.
If I issue a letter, should it be back dated or can it be as on date?
Pls confirm.

Your MD's has communicated his new roles and responsibilities through the email you may take copy of this email and issued to him and also communicate to your employees through notice board.
P. Xavier Raj

Dear Divya,
For change of designation or roles responsibilities, it is important to issue it on the company letterhead. Now you can issue this letter letter as follow up to the earlier mail. It need not be back dated. Attach copy of the e-mail to this letter.
Apprise your MD, albeit gently that he need not rush this jobs through e-mails. He can show patience of giving formal letters.
Ok...
DVD

Thanks Dinesh. The issue was also that there was no HR at the time of this announcement as the earlier HR happened to go on a medical emergency and I have joined only recently.
Nevertheless, I shall have a word with MD and issue a formal letter to the concerned employee.

Hi Divya,
If a candidate designation has changed,A letter should be given to him and explain the new roles and responsibilities.An internal copy should be sent to all top level managers to announce.

Dear Divya,
Thanks for the feedback. Hardly any member shows courtesy of this kind to give feedback after implementation of some suggestion or advice. Kudos to you!
DVD
Thanks Jinson,
I have issued the letter yesterday to the concerned employee :)