Direct mail is a dependable way for businesses to reach customers. Even with the growing use of digital ads, traditional direct mail still delivers strong response rates because physical mail stands out. Postcards, printed newsletters, and self-mailers can’t be deleted with a click.
The confusing part of direct mail is navigating the rules set by the U.S. Postal Service. These rules affect size, layout, preparation, postage, and even how your piece is sorted. Our direct mail experts at Custom Printing will help you understand the fundamentals so your mail campaigns move smoothly from design to print to the post office.
Mail piece size is the first thing to get right
USPS places every mail piece into a size category. The three most common for marketing are postcard, letter, and flat. Each category comes with specific minimum and maximum dimensions, and each category has its own postage rate. Even a small change can bump your design into a more expensive group.
A standard postcard is between 3.5 by 5 inches and 4.25 by 6 inches. Pieces that are larger, like 6 by 9 or 6 by 11 postcards, fall into the letter category. Anything beyond 6.125 by 11.5 inches becomes a flat. That shift affects postage because flats cost more to sort and deliver. For an overview of common formats, USPS provides size standards on its Business Mail 101 site.
Address placement and clear zones are more important than most customers realize
USPS automated sorting machines scan both the address and the routing barcode. If your design places graphics, heavy color, text, or patterns too close to these scanning areas, your mail may lose automation eligibility or even be rejected. Automation eligibility matters because it qualifies your mailing for lower postage.
The most critical area is the lower right section of the address panel. Keeping this region clear helps the machine read the barcode. Dark backgrounds, overlapping graphics, or complex patterns in the clear zones often cause issues.
Custom Printing reviews address layouts during proofing to catch these issues early. If you want to see USPS guidelines for yourself, they are outlined in the USPS addressing standards.
Folded pieces, tabs, and paper thickness also affect acceptance
Folded self-mailers follow a separate set of postal rules. These include the direction of the fold, the location of the opening, and the required number of tabs or wafer seals. A basic tri-fold self-mailer needs two tabs if mailed without an envelope. Paper thickness matters and how your mailer is folded also matters. If your stock is too thin or too thick for the category you selected, the piece may be rejected or reclassified.
Automation pricing for letters and cards
Automation pricing is the discounted postage rate USPS offers when your mailing is easy for their machines to sort. To qualify, your pieces must follow specific rules for addressing, barcoding, tabbing, thickness, and sorting. We handle most of this during production, but the accuracy of your mailing list affects whether you get the lower rate.
A clean list with updated addresses improves deliverability and helps maintain automation eligibility. Custom Printing uses address verification tools when preparing mailings, but keeping your list updated is still one of the easiest ways to save money. If you need to verify individual addresses, USPS offers a free ZIP Code Lookup tool.
Choosing between EDDM and targeted direct mail
Every Door Direct Mail (EDDM) works well when your goal is to reach every household in selected postal routes. You do not need a mailing list. USPS delivers to every residential address along the chosen route. The service has its own rules for size, bundling, and paperwork. EDDM is commonly used by restaurants, real estate agents, home service companies, and gyms.
Alternatively, targeted direct mail uses a mailing list and gives you more control. You can reach specific individuals or businesses based on demographics, geography, income, home value, industry, or buying behavior.
Early planning prevents most problems
Most mailing issues happen when a design is already finished and someone discovers that the size, address placement, or paper does not meet postal requirements. Fixing these problems late in the process can delay the job or increase postage.
When you confirm size, leave room for the address panel, select mailing-friendly paper, and follow USPS clear zones, your mail gets printed and accepted without surprises.
Custom Printing checks all these details during the proofing and prepress stages. With a little early planning, the entire process becomes smoother. Postage stays predictable, turnaround times stay reliable, and your message reaches the audience you intended.
What’s New in Post Regulations for 2026
Most postal rules stay consistent year to year, but there are a few changes taking shape as we move into 2026 that you should know about. None of these change the basics of how you design or prepare a mail piece, but they do affect planning, timing, and list quality.
USPS is in discussions about tightening certain folded self-mailer requirements. This includes clearer rules about tab placement, how certain multi-panel folds are handled, and minimum paper weights. If you like creative layouts or heavier cover stocks, it is worth confirming that your design still qualifies for automation rates.
USPS is expected to continue semiannual rate adjustments, based on recent patterns. This pattern has been steady for several years, with changes in January and July. For businesses that run multiple mailings a year, building rate changes into the annual marketing budget will make planning easier.
Address quality standards are getting stricter. Under the newer CASS requirements, lists with missing apartment numbers, incorrect directional indicators, or incomplete fields will see more delivery failures. Keeping your lists clean is one of the simplest ways to keep postage costs down and improve deliverability.
Move Update compliance is becoming more widely enforced across more mail classes. If you mail without NCOA or other approved address updates, USPS can reclassify your mailing or add extra charges. This change especially affects Standard Mail letters and flats.
EDDM route data is also improving. USPS is updating counts more frequently and identifying residential and business addresses more accurately. This will make planning local saturation mailings a little more reliable in 2026.
These changes are not difficult to navigate, and Custom Printing builds them into every mailing project we produce. If you want help planning a 2026 mailing schedule or need guidance on a specific format, we can walk you through the details before you start designing.