Bilateral treaties concerning the international postal services were numerous and rarely consistent. By 1874, Germany had 17 postal agreements, France 16, Belgium 15 and the United Kingdom 12. Depending on the routes used to send the mail, it could trigger elements of several postal agreements, stacking up the respective charges for each area the cover traveled through.
Additionally, countries used different weight measures: USA and UK: ½ oz; France: 10 grams until 1 July 1870 and thereafter 15 grams; Germany ... Thus a ½ oz letter from the USA would be easily computed through the United Kingdom at the same rate, but when it arrived it France it would be at the second rate. A calculation of rates for the countries in attendance at the Berne Conference in 1874 totaled 1.200 different rates for mail.
Postmaster General Montgomery Blair, of the United States, reported to Congress in his annual message of 1862 that "...the whole system, as now established, is too complex to be readily understood by postmasters. Our International mail system is extremely loose and defective. There is no common standard weight for the single rate. There is no common rate for the sea transit or for overland transit. The inland transit rate upon domestic correspondences furnishes no rule for the overland transit of foreign correspondence. Rates upon closed mails are not uniform by distance, or by other common rule and they vary greatly according to the route of carriage."
For the reasons of this chaos, the Postmaster General of the United States called for an international postal congress that took place in Paris from 11 May till 8 June 1863.
This first meeting of postal administrations from around the world (Austria, Belgium, Costa Rica, Denmark, Ecuador, Spain, France, Great Britain, Italy, Netherlands, Portugal, Prussia, Hawaii, Switzerland, USA and the Hanseatic cities) concluded with these objectives of future international postal agreements:
Reduction of rates on international mail, printed and written
Reduction or abolition of transit fees for closed mails (a lucrative business for some countries at the cross-roads of global mail flow)
Establishment of uniform international postal rates
Simplified and uniform rules governing the exchange of correspondence among countries.
This congress definitely influenced negotiations in nearly all subsequent bilateral agreements - at least among the conference participants. The Paris meeting of 1863 was the most important starting point for the eventual first meeting of the General Postal Union in Berne in 1874; a meeting delayed for years by the growing hostilities and eruption of wars involving several European powers, culminating in a war between France and the German states (Franco-German War of 1870-1871).
In 1963 almost all the countries that attended the Conference issued commemorative stamps to celebrate the centenary of this first international brainstorm.
Stamp catalogue - centenary