Can I use a 4" × 6" postcard for EDDM?

No, a 4" x 6" postcard cannot be used for EDDM. It falls short of the USPS minimum of 6.125 inches on the shortest side, so it does not qualify for saturated mailing rates and will be rejected at the post office.

• The problem: the 4-inch short side is below the 6.125-inch EDDM minimum.
• The result: it is treated as a standard postcard, not an EDDM piece.
• The fix: design at 6.5" x 9" or larger for EDDM eligibility.

If you want the low, per-route EDDM postage, start your design at the qualifying size rather than trying to force a small card through the program.