A post office is a public facility and a retailer that provides mail services, such as accepting letters and parcels, providing post office boxes, and selling postage stamps, packaging, and stationery. Post offices may offer additional services, which vary by country. These include providing and accepting government forms (such as passport applications), and processing government services and fees (such as road tax, postal savings, or bank fees). The chief administrator of a post office is called a postmaster.
Before the advent of postal codes and the post office, postal systems would route items to a specific post office for receipt or delivery. During the 19th century in the United States, this often led to smaller communities being renamed after their post offices, particularly after the Post Office Department began to require that post office names not be duplicated within a state.
The term "post-office" has been in use since the 1650s, shortly after the legalisation of private mail services in England in 1635. In early modern England, post riders—mounted couriers—were placed, or "posted", every few hours along post roads at posting houses (also known as post houses) between major cities, or "post towns". These stables or inns permitted important correspondence to travel without delay. In early America, post offices were also known as stations. This term, as well as the term "post house", fell from use as horse and coach services were replaced by railways, aircraft, and automobiles.
The term "post office" usually refers to government postal facilities providing customer service. "General Post Office" is sometimes used for the national headquarters of a postal service, even if the building does not provide customer service. A postal facility that is used exclusively for processing mail is instead known as a sorting office or delivery office, which may have a large central area known as a sorting or postal hall. Integrated facilities combining mail processing with railway stations or airports are known as mail exchanges.