Using older versions of Outlook for Mac in business environments
Excellent workaround, it works and what it does is to save a Draft of the initial message which does not allow to type the recipient address on the Field "To", then open a new window and on this new message you can type the address as it supposed to be. So at the end is the same result as the other workaround which suggest to save the original message as a draft and open a new one.
Who's failure is this from Microsoft or Apple or both? so please whoever are responsible please fix this bug as soon as possible and let us know.