Pursuant to the UPU's mission, each member state agrees to the same terms for conducting international postal duties.

Since there was no postal treaty between the United States and France, the mail had to travel on a British or a Belgian ship.

Elihu Washburne, the new US Minister to France, arrived in Paris in 1869 to find "the singular spectacle ... of no postal arrangements between two countries connected by so many business and social relations.

United States Postmaster General Montgomery Blair called for an International Postal Congress in 1863.

Meeting in Paris, the delegates laid down some general principles for postal cooperation but failed to come to an agreement.

[note 2] After the General Postal Union was established, its membership grew rapidly as other countries joined.

The majority of the UPU's documents and publications—including its flagship magazine, Union Postale—are available in the United Nations' six official languages: French, English, Arabic, Chinese, Russian, and Spanish.

[15] Toward the end of the 19th century, the UPU issued rules concerning stamp design, intended to ensure maximum efficiency in handling international mail.

[16] Another required member nations to use the same colors on their stamps issued for post cards (green), normal letters (red) and international mail (blue), a system that remained in use for several decades.

The problem of imbalanced flows became acute after decolonization, as dozens of former European colonies entered the UPU as independent states.

[20] Since the Executive Council had been unable to come up with a cost-based compensation scheme after five years of study, terminal dues were set arbitrarily at half a gold franc (0.163 SDR) per kilogram.

Since the terminal dues were fixed, low-cost countries that were net recipients would turn a profit on delivering international mail.

To protect its profits on sending international mail, the United States voted with the developing countries to keep terminal dues low.

At the time, the UPU's Postal Development Indicator scale was used to classify countries into four groups from richest to poorest.

[25]: 38  The Presidency of Donald Trump complained that it was "being forced to heavily subsidize small parcels coming into our country.

"[26] On 17 October 2018, the United States announced that it would withdraw from the UPU in one year and self-declare the rates it charged to other postal services.

[27] The Universal Postal Union responded in May 2019 by calling, for only the third time in its history, an Extraordinary Congress for 24–26 September 2019.

[28] The members voted down a proposal submitted by the United States and Canada,[29] which would have allowed immediate self-declaration of terminal dues.

In addition, countries receiving more than 75,000 tonnes of mail—currently only the United States—could opt in to accelerated self-declared terminal dues on 1 July 2020 in return for an $8 million annual "contribution" to the UPU for five years.

[31] Trump adviser Peter Navarro declared that the agreement "more than achieved the President's goal,"[32] but he denied that the United States was "buying" the deal with its "contribution".

[31] UPU Director Siva Somasundram hailed the agreement as "a landmark decision for multilateralism and the Union.

The Standards Board ensures that coherent regulations are developed in areas such as electronic data interchange (EDI), mail encoding, postal forms and meters.

[42] However, its bid for membership was defeated in September 2019 by a vote of 56 in support, 23 abstaining, 7 countries in opposition, and 106 countries not responding to the request to vote (which, according to UPU rules, led them to be tallied as abstentions)—leaving the bid substantially short of the required two-thirds majority of UPU members.

Many of them have images, which generally remain copyrighted by the issuing country, but the UPU and WADP permit them to be downloaded.

[48][49] Developing their own standards, the UPU expects to unveil a whole new range of international digital postal services, including e-post.