Buying Tickets by post

I normally buy my away tickets by post, but today I find out that postal applications for tickets have to be accompanied by the full 16 digit credit card number AND the 3 digit security number on the rear of the card. This seems mightily scary on the security front. Surely those two numbers should never be written down together? Will you be asking us to send you our PINs next?

Please could you confirm whether this is the case or not.