我的如下这段代码即使邮件发送不成功，也会创建一个新的 post，请问如何如果投送邮件失败，将这条 post.save rollback 呢？

def create
  @post = post.new(post_params)
  @post.user = current_user
  if @post.save
    begin
    AppMailer.notify_on_new_post(current_user, @post).deliver
    flash[:notice] = 'Post Created'
    rescue Exception
      flash[:error] = 'Oops, problems sending the mail'
    end
    redirect_to user_path(@post.user)
  else
    render :new
  end
end