How we check things

Every postal rule on this site is checked againstUSPS Publication 28, the document the Postal Service writes for professional mailers. When a page says the bottom strip of the envelope has to stay clear, that is not a tip someone heard once. It is a measurement from the manual.

For addresses we are not sure about, we check them against the Postal Service's ownZIP Code lookup tool, the same one you can use before mailing anything important.

Etiquette is different. There is no manual, and the old books disagree with each other. Where a rule is about manners rather than machines, the page says so plainly and tells you what most people do now.

Every page shows the date it was last checked. When the Postal Service changes a rate or a rule, the pages that mention it get updated and the date moves.