sure. its when the first person mails off coupons that they can't use/don't want to the next person who takes out the coupons from the envelope that they can use/want, and replaces them with coupons they have that they don't want/can't use. and then mails the envelope off to the next person on the list. and so on. and then the final person mails it back to the first person.
we could do coupons for products available in canada.
what do you think?