Yes do not forward is written on envelope .I forwarded my mail also to my new address but Canada post returned it back to immigration . I was checking with immigration every week if they received back from Canada post or not. I took almost 1 month to get my card on new address.
Thank you very much for letting me know! Did you submit a Solemn Declaration to get your card back from CIC? Or CIC just sent back the first card once they received it?