Correo Argentino, the mail service, has an office in most towns or city neighborhoods; some locutorios also serve as collection points and sell stamps. Older postboxes are dark blue and yellow, newer ones dark and light blue: most are found either inside or directly outside post offices. Mail delivery isn't dependable: it can take 6 to 21 days for standard letters and postcards to get to the United States. Regular airmail letters cost 19 pesos for up to 20 grams.
If you want to be sure something will arrive, send it by correo certificado (registered mail), which costs 52 pesos for international letters up to 20 grams. Valuable items are best sent with express services like DHL, UPS, or FedEx—delivery within one to two days for a 5-kilogram (11-pound) package starts at about 2,000 pesos. A similar size package would cost 670 pesos to send with Correo Argentino and would take up to a week to arrive.
Argentina's post-code system is based on a four-digit code. Each province is assigned a letter (the city of Buenos Aires is "C," for instance) that goes before the number code, and each city block is identified by three letters afterward (such as ABD). In practice, however, only big cities use these complete postal codes (which look like C1234ABD; the rest of Argentina uses the basic number code (1234, for example).
Correo Argentino. www.correoargentino.com.ar.