I mailed the envelopes at the "Vaunargues" Post Office on the rue Marcadet, in Paris' 18th arrondissement. Years ago, I would have bought the envelopes up to a clerk, who would have weighed them, decorated them with colorful stamps and placed them in a bin behind the desk. Now, there is a self-service machine whose stamps bear only the mark of the sum I pay printed on them.
After affixing a stamp to each envelop in the bunch of pieces I sent on a particular day, I walked outside to deposit my mail in one of two slots: "Paris and banlieue" or "Province /Etranger." I notice how the white envelopes glow against the blue and gold facade of the post office; perhaps the post office determined my choice of colors for the art.
Several of the letters never made it to their destinations.
One of the envelopes I mailed was returned to me a couple of months later. I sent it once again, hoping it would reach its destination. I got a "traceable" stamp this time
5 April 2021
30 April, 2021: Checking up on the letter sent 12 April
The website of La Poste allows you to track the movement of letters. I saw that the letter addressed to the UAE seemed to have been sent to the USA. I tried to request assistance from the post office help site. It tooks some time to enter all of the numbers and proof of my receipt. I received a message saying that my request could not be processed "right now." I was supposed to "try again later."