The most common EDDM mistake happens before a single card is mailed: printing a postcard that's the wrong size. Every Door Direct Mail® has its own size rules, and a postcard that travels fine as regular mail can be turned away as EDDM.
Here's what USPS requires, why the rules work the way they do, and how to check your design before it goes to print.
The short version: EDDM pieces must be flats
USPS treats EDDM postcards, flyers and menus as USPS Marketing Mail® flats (USPS). A flat is a piece that's bigger than a letter in at least one dimension. Small postcards are letter-size mail, so they don't qualify.
That's the reason EDDM postcards are noticeably larger than the cards you'd send to a friend. The size isn't a style choice. It's what makes the piece eligible.
What makes a piece "letter-size"
The USPS Domestic Mail Manual (DMM) sets the limits for letter-size mail. A letter-size piece is no more than (DMM 101):
- 11-1/2 inches long,
- 6-1/8 inches high, and
- 1/4 inch thick.
If your piece fits inside all three of those limits, it's a letter. To be a flat, it has to go past at least one of them.
EDDM Retail size rules
EDDM Retail® is the version you set up through a USPS.com account and drop off at the Post Office. Its rules are in DMM section 143. As of October 2026, an EDDM Retail flat must (DMM 143):
- Weigh no more than 3.3 ounces, and
- Meet at least one of these: longer than 10-1/2 inches, or taller than 6-1/8 inches, or thicker than 1/4 inch.
Notice the length figure. For EDDM Retail, DMM 143 uses 10-1/2 inches for length, not the 11-1/2-inch letter limit. Height and thickness use the same numbers as the letter limits. If you're reading older guides or printer templates, check them against the current DMM rather than assuming they match.
For example, a piece 6-1/4 inches high qualifies on height alone, whatever its length. A piece only 6 inches high would need to be longer than 10-1/2 inches (or thicker than 1/4 inch) to qualify.
Maximum size
Flats also have an upper limit. A flat-size piece can be no more than 15 inches long, 12 inches high and 3/4 inch thick (DMM 101). DMM 143 points back to these general limits for EDDM Retail.
Other physical rules
The DMM also says flat-size pieces must be (DMM 101):
- Rectangular, with square corners or rounded corners no larger than a 1/8-inch radius.
- Flexible. Boxes and rigid pieces aren't flats.
- Uniformly thick, so bumps or attachments don't cause more than a 1/4-inch difference in thickness.
A standard printed postcard meets these easily. They matter more if you add a magnet, a sample or a fold.
EDDM BMEU mailings
EDDM BMEU is the larger-volume option, entered at a Business Mail Entry Unit with a bulk mailing permit and no volume limit (USPS). The USPS price it lists ("as low as" $0.259 per piece as of October 2026) is for Marketing Mail flats up to 3.3 ounces.
The flat idea is the same: USPS Marketing Mail pieces with simplified addresses must have at least one dimension larger than the letter-size maximum (DMM 602). Because BMEU mailings follow commercial standards, have your mailing service or the BMEU confirm the exact requirements for your piece.
Weight: the 3.3-ounce line
USPS lists its EDDM prices for flats up to 3.3 ounces (USPS), and EDDM Retail flats can't go over that weight (DMM 143). A single postcard is far below it. Weight becomes a question with thick folded mailers, multi-page menus or anything attached to the card.
Space you have to leave on the design
Size isn't only about the outer edges. Every EDDM Retail piece needs room for the indicia (the postage marking). As of October 2026, USPS says (USPS):
- The EDDM Retail indicia goes above and to the right of the address block.
- It must be larger than 0.5 by 0.5 inches, with type in all caps at 4 point or larger.
- It should fit in the area 1.625 inches from the right edge and 1.375 inches from the top edge.
- Leave 1/8 inch of space around its top and right edge.
EDDM pieces don't carry names and street addresses. They use a simplified address such as "Postal Customer," which tells the carrier to deliver to every address on the route (DMM 602). Plan the mailing side around the indicia and address block first, then fit your message into the space that's left.
How to check your design before you print
- Measure the finished size. Check length, height and thickness against the rules above. One dimension past the line is enough.
- Use the USPS Mailpiece Size Checker. USPS offers it in the EDDM Online Tool to confirm a flyer or postcard meets the requirements.
- Check the weight if your piece is folded, has extra pages or has anything attached.
- Leave room for the indicia and address block before placing your headline and photos.
- Re-check the DMM if you're using an old template. USPS updates its standards.
Printing and mailing with PostcardDrop
PostcardDrop prints and mails EDDM postcards for you, starting at 50¢ per postcard with printing and postage included. The price varies by ZIP code and is confirmed in your quote, with a 2,500-piece minimum. Learn more on the EDDM postcards page, or estimate a mailing with the EDDM cost calculator. If you're still working out the budget, see how much EDDM costs.
Sources: USPS Domestic Mail Manual 143, EDDM-Retail Prices and Eligibility (checked October 2026); USPS Domestic Mail Manual 101, Physical Standards (checked October 2026); USPS Domestic Mail Manual 602, Addressing (checked October 2026); USPS, Using Every Door Direct Mail (prices, indicia and Size Checker, checked October 2026). USPS rules and prices can change; confirm current details with USPS before you print.
Want postcards in mailboxes without the hassle? PostcardDrop handles printing, postage and drop-off: EDDM starts at 50¢ a piece, depending on ZIP code (2,500 minimum), and targeted mail is $1.10 a piece. Estimate your cost or see how EDDM works.