Most postage surprises come from the list, not the artwork. A file that looks fine in a spreadsheet can still fail to qualify for the prices you budgeted. Here is what a mailable list needs and how to get there.
Start with the file itself
Provide the list as a CSV or Excel file with one record per row and clear, separate columns: full name, company if relevant, address line 1, address line 2 or suite, city, state, and ZIP. Keep the headers consistent and avoid merged fields, because a single "address" column containing everything has to be split before anything else can happen.
Column names themselves can vary. What matters is that each piece of the address lives in its own column.
Run CASS processing
CASS processing standardizes each address against USPS data, validates it, and appends the ZIP+4 and delivery point information. That appended data is what makes a valid Intelligent Mail barcode possible, and the barcode is what earns automation prices.
An address that fails CASS cannot claim automation pricing and may not be deliverable at all. This step is not optional if price matters.
Meet Move Update
Mailings claiming presort or automation prices for First-Class Mail and USPS Marketing Mail must be Move Update compliant, using an approved method such as NCOALink, within 95 days of the mailing date. This updates addresses for people who have moved.
Noncompliance can cost you the discount and trigger an assessment, so it is worth confirming rather than assuming.
Deduplicate and household
Deduplication removes repeated records so the same person is not mailed twice. Householding combines multiple recipients at one address into a single piece where that is appropriate for the campaign.
Both reduce waste directly. On a large list they often pay for the processing several times over.
Check the quantity against the minimums
Presort and bulk prices need minimum volumes. First-Class Mail presort requires at least 500 pieces. USPS Marketing Mail requires at least 200 pieces or 50 pounds, whichever comes first. Below those thresholds, single-piece retail prices apply.
Know what the list actually qualifies for
How deeply a list sorts, and therefore how low the price goes, depends on how the records concentrate into ZIP areas. A list of 5,000 spread thinly across the country sorts differently than 5,000 concentrated in a handful of ZIP codes, even though the piece counts match.
That is determined at processing, not estimated by eye. Running the list first is the only way to build a budget on real numbers.