In order to be accepted by the USPS for mailing, your EDDM postcards must be bundled in stacks of 50 or 100. Each stack cannot exceed 6 inches in height, and bundles should be consistent. Consistent bundling means that you use only groups of 50 or 100, not a mix of the two. For example, if you have 588 postcards, you could put together 11 bundles of 50 and one bundle of 38 or five bundles of 100 and one bundle of 88. If you place your print order with us, we can bundle your postcards in groups of 100 - one less thing to think about!