Distinguish new mail compose and reply?

Hello,

Is there any way I can set different parameters when composing a new
mail or composing a reply? AFAIK the message-mode-hook() gets called
in both cases. For example, I want to set "use-hard-newlines" when I
am writing a new mail, but don't want to send it when I am replying.

regards
Kousik Nandy