The Universal Postal Union establishes international regulations for postal services, provides technical assistance and promotes cooperation in postal matters.
Blas Delgado Ortiz, 24 June 2000
Apparently the UPU adopted a new logo (but not a new flag) this logo replaces the prior logo:
"A resolution authorizing the UPU to officially adopt the emblem that appears on its flag as its new logo was approved. The new UPU logo will consist of the current UPU logo (showing a detail from its monument in Berne) with the United Nations olive branches around it "
UPU itself shows its flag with the new emblem and says it was adopted in 1948.
The emblem depicts five men and women, among which is an American Indian ("a native American") who dance round around a sphere. The sphere is the Earth and the five men and women represent the five continents. The emblem is surrounded by the UNO laurel branches. These are all in white and appear in the middle of a plain blue (UNO-ONU) flag. Proportions: 2:3.
Nordisk Flaggkontakt 42 shows a blue flag with a smaller white logo between two white laurel wreaths. The article was written by Jan Oskar Engene, and the image above showing only the logo, may be wrong. Note however, that the official site of IAEA also shows the UPU flag without leaves