The Universal Postal Union (UPU) a international organization that coordinates postal policies between member nations, and hence the world-wide postal system. Each member country agrees to the same set of terms for conducting international postal duties.
Prior to the UPU, a country would have to have a separate postal treaty for each country that it wished to carry international mail to or from. The United States called for an international postal congress, which was held in 1863. This led to the creation of the Universal Postal Union, the oldest international organization and was created in 1874, under the name "General Postal Union," as a result of the Treaty of Berne signed on October 9 1874. In 1878 the name was changed to "Universal Postal Union."
The UPU established that (1) there should be a more or less uniform flat rate to mail a letter anywhere in the world; (2) postal authorities should give equal treatment to foreign and domestic mail; and (3) each country should retain all monies it collected for international postage.
One of the most important results of the UPU has been that it is no longer necessary, as it often was previously, to have stamps of any country through which one desired transit of one's letter or package, affixed to it; the UPU provides that stamps of member nations are accepted for the whole international route.
In 1969 the UPU introduced a new system of payment , by which fees were payable between countries on the difference in the total weight of mail between the respective countires. These fees were called terminal dues.
As this affected the cost of the delivery of periodicals, the UPU devised a new "threshold" system, which was implemented in 1991. The system sets separate letter and periodical rates for countries which are sent at least 150 tons of mail to annually. For countries with less mail, the original flat rate has been maintained. The United States has negotiated a separate terminal dues formula with 13 European countries that included a rate per piece plus a rate per kilogram, and has a similar arrangement with Canada.
The UPU also operates the system of International Reply Coupon.