Some might think that it is the message, the colors, the paper and a variety of other things but the most important thing is the addressing area. The mail piece can be brilliantly designed, have a great message and have excellent printing but it will never reach the intended recipient if it is not addressed correctly. There is a lot of space on the mailing panel that can be used for copy, but a certain area must be left for the address and applying the intelligent bar-code. Not leaving enough room for addressing is one of the most common mistakes that I see. On a 4×6 card, there is not much room for copy because of the small size. I recommend the 5.5×8.5 size post card because it gets more attention when received and it gives room for addressing and more copy. This is true for a fold over mailer or newsletter.
If Burns is designing the mail piece you don’t have to worry about USPS regulations, we have that covered. If we are not designing the mail piece, we provide templates, to our customers, so that they know how much room is needed on the mailing panel.