GLOSSARY
Service standard
By Justin Winter · Updated August 28, 2026
USPS’s published expected delivery time for a mail class — a target measured in business days, not a guaranteed date.
Service standards are how USPS states expected performance: a First-Class letter is expected to arrive within a stated number of business days of acceptance, and performance against that target is reported in aggregate.
The practical consequence is that any estimated arrival window is an estimate. Priority Mail Express is the only product that turns a date into a guarantee.
See also
- First-Class Mail — The everyday USPS class for letters and documents — typically 3–5 business days, with no tracking unless you add it.
- Priority Mail — A faster USPS class — typically 1–3 business days — with tracking included as standard.
- Priority Mail Express — USPS’s fastest tier, overnight to most addresses with a money-back delivery guarantee. paperplane does not offer it.
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