USPS shipping guide

USPS Shipping & Mail Products: Overview

The United States Postal Service handles letters, flats, and many parcel products (Priority Mail, Priority Mail Express, Ground Advantage, Media Mail where eligible, and international options). This page is a research primer.

Strengths people cite

  • Nationwide delivery to every address, including many PO Boxes
  • Retail access via post offices and approved partners
  • Letter-mail monopoly services that private carriers do not replace
  • Flat-rate packaging options that simplify quoting for some sizes

Know eligibility rules

Media Mail has content restrictions. Hazardous materials rules apply. International forms (customs declarations) must match contents. Using the wrong product can mean postage due or return to sender.

USPS vs private carriers for parcels

USPS can be cost-effective for light packages to residential addresses. Heavy or time-critical B2B freight may fit UPS/FedEx better. Test real weights on official calculators.

Relationship to mailboxes

PO Boxes and CMRA private mailboxes both interact with USPS delivery rules. See private mailbox vs PO Box and Form 1583.

We are not a USPS retail unit and do not sell postage.

Click-N-Ship and retail differences

Online postage and retail counter postage can differ in price and available products. Cubic pricing may help dense packages under size limits. Always validate address quality to reduce undeliverable-as-addressed returns.

PO Box delivery quirks for private carriers

UPS and FedEx generally cannot deliver into a USPS PO Box. If your recipient only lists a PO Box, choose USPS or obtain a street address. This is a common failure point for marketplace sellers.

Further reading

Explore related explainers via the main navigation: private mailboxes, virtual mailboxes, shipping carrier overviews, packing tips, and document service basics. Each page states what we do not offer so you can trust the boundary between education and commerce.

If something on this page is outdated, please email a correction with a link to an official source. We revise articles when carriers or agencies publish material changes that affect consumers.

Authoritative sources

Verify current rules and product details on official sites:

Capital Postal Mailbox publishes educational guides only and does not fulfill retail postal or shipping services.