Repopulating form after validation error

that should work just fine provided you don't do a redirect in your controller upon failure... you need something like

MyController

  def send_mail

    if request.post?       if everything validates etc         flash[:notice] = 'Message sent'         redirect_to :action => :message_sent       else         render :action => :contact_form       end     end

  end

end

note that if there was an error you render an action, not redirect to it. if you redirect you are responsible for preserving all params yourself.