They are available in post offices or via home delivery from the La Boutique – particuliers (members of the public, as opposed to business) section at laposte.fr
These are suitable for sending an ordinary letter (up to 20g) within France, securely and with proof of posting and of receipt by the person you are sending it to.
You place the letter in the envelope and write on the recipient’s address, then open the application on your phone.
Following the instructions for sending a recorded delivery letter, you take a picture of the bar code on the back of the envelope, put in sender and recipient’s address and click valider.
You then either drop the letter to a teller at your post office, or into a dedicated box.
You can then follow the delivery progress on your phone and are automatically informed when it has been delivered.
The reception slip is sent in electronic form that you can also view on your mobile phone.
Another handy way to send a letter by recorded delivery, which avoids going to the post office, is the entirely online service (tinyurl.com/OnlineLR) which involves attaching a computer document from your files, which is then printed out and delivered for you by the postal service.