One of the most common mailing mistakes that I see, is not checking the USPS specification before printing. There are certain areas on a post card that you can put copy and certain areas that must be left for addressing. The area that must be left for addressing changed when the USPS implemented the intelligent bar-code. The intelligent bar-code is much larger because it contains more information that the USPS uses to process the mail. One benefit is that it speeds delivery and if the list is sorted correctly and the bar-code applied it can save money on postage. There are other common mistakes such as the orientation of the mailing panel, the weight of the paper and even the color of the paper.
That is why I recommend consulting with the experts at the inception of your direct mail project. At Burns consulting is FREE to our customers. We also provide templates for post cards and mailers so that our customers know what area they can use, on the mailing panel, to get their message across to their target market.