Direct mail basics

City limits vs. ZIP codes: when a list beats EDDM for precision

Postal routes follow ZIP codes, and ZIP codes ignore city lines. Here is what that does to a city-wide mailing, three ways to stay inside the line, and the point where an address list costs less than every door.

Published Sat, Oct 17, 2026 · Updated Fri, Oct 23, 2026

• EDDM
• Mailing lists
• Data sources
• Florida
• Broward County
• Costs

If your audience is a whole city, its limits are the line that matters, and the Postal Service does not draw that line. This guide explains why a mailing by postal route spills into the next town, and how to keep it inside. For the three ways to reach homes, start with Direct Mail 101.

ZIP codes follow mail routes

A ZIP code is a delivery area. The Congressional Research Service puts it this way: "Postal ZIP codes do not always align with recognized municipal boundaries" because they follow "mail routes and delivery points" (CRS IF12132).

Every Door Direct Mail is built on those routes. USPS prepares an EDDM Retail mailing by delivery route within a five-digit ZIP (DMM 145.1.3), its tool names each route by ZIP and route number (33301-C001), and city limits never appear in it. The same goes for list vendors' "city" selects, which use the postal city name on the address. A home with a Davie mailing address can sit in another town.

What that does to a city race

We mapped this for the Town of Davie in Broward County. No ZIP code is Davie-only. Across the eight ZIPs that carry Davie addresses, there are 103,582 addresses on 151 routes, and by our estimate about 42,640 of them, roughly 41%, are in the town.

Take one ZIP, 33328. It has 18 routes and 11,641 addresses. About 7,617 of them are in Davie and about 4,024 are in Cooper City. Mail the whole ZIP and roughly one piece in three lands in a town whose voters can't vote in Davie's race.

These are our estimates, made by laying each route over Census town boundaries, and the counts include businesses. A route that crosses the line counts toward whichever town holds most of it.

Three ways to stay inside the line

1. Pick routes against the boundary map, and accept some spill. Open the USPS route tool beside your county's municipal boundary map and keep the routes that sit mostly inside town. Broward (Municipal Boundaries) and Palm Beach (Municipal Boundaries) publish theirs free. Broward's carries the note "Not to be used for legal boundary determinations", which is fine for picking mail routes. For Davie, keeping only the routes that are mostly in town gave us 58 routes and 42,826 addresses, with an estimated 5 to 10% outside the line. Our guide to picking EDDM routes walks through the tool.

2. Cut the county tax roll to the city. Florida's Department of Revenue publishes every county's property roll as a free download (Florida DOR). Each parcel carries a taxing-authority code, "a code identifying the taxing authorities whose jurisdictions include the parcel", and municipalities are among those authorities (2026 NAL User's Guide). Filter on your city's code and you have every parcel inside the line, with the owner's name and the property address. The codes differ by county, so ask the property appraiser which one is your city.

3. Buy a list cut to a drawn shape. Several list vendors let you draw the area on a map. Click2Mail's list tool offers a "Custom Polygon" (Click2Mail), and Mailers Haven sells occupant data with "Polygon mapping technology for custom territory drawing" (Mailers Haven). Trace the city boundary and you get the addresses inside it.

For a campaign there is a fourth source, the voter file, which carries each voter's precinct and districts. Our voter list mail service works from it.

Round counts

A list is exactly as big as the area you cut. If 7,617 homes in a ZIP are inside town, a list of them has 7,617 addresses.

EDDM is whatever the routes add up to. You take each route whole, so the count is the sum of the routes you picked, and you can't trim a few houses off the end to hit a budget. Plan the print run around the route total.

The price of precision

A list costs more per piece than EDDM. Addressed mail pays higher postage, and the list has to be cleaned and addressed. The question is whether it costs more per home you actually want.

Using our 10,000-piece prices as the yardstick, with a 6.5" × 9" EDDM card and our 6" × 9" list postcard:

EDDM postage is the USPS retail rate. List postage is billed at the actual USPS rate after presort, usually 29¢–40¢ per piece.

Now divide by the share of pieces that reach the homes you want. Mail all of ZIP 33328 by EDDM and only about 65% of pieces land in Davie, so each Davie home costs about 72¢. A list cut to Davie's addresses costs 57¢ to 68¢ per home, because every piece is a Davie home. In that ZIP, the list wins.

The rule of thumb from those numbers: when fewer than about 69% of the homes on your routes are inside the line, a list costs less per in-town home. Above about 82%, EDDM does. In between, it depends on how densely your list sorts. Add the cost of the list itself: the tax roll is free, and a vendor's occupant list runs about a penny a record by the published prices (mailing lists explained).

Or let us do it

You can do all of this yourself with the USPS tool, a boundary map and the tax roll. If you would rather hand it off, send us your city and we will price both ways, the best set of routes and an address list cut to the city line, so you can see which one costs less per home. Or go straight to EDDM pricing.

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