I post 10 cased CDs a day so it was vital they got to my customer undamaged.The best way to do this is of course via a cardboard CD box, however they do have the problem that the weight of a single cased CD and box goes over 100 gram, the solution to this is use a padded envelope, however this is not as strong and there will be breakages.I have found JL0 Jiffy Airkraft the best thing to use to reduce breakages, in addition make sure when you place the CD in the envelope to put it in to the back of the envelope and then to seal it up as tight as possible.
It has worked fine with me I hope it helps you as well and saves you a lot of time and effort and of course happier customers.