All your messages are shown in your personal inbox on La Récup'. There you can reply to any messages you have received. 

To access your personal inbox, you must be logged in. Please click on the envelope icon in the main menu or on "Messages" in the submenu under the person icon in the main menu. You can also go to  

On a computer: 

Or, on a mobile phone:

To send a message to a person in response to an ad, please click on "Send message" at the bottom of the ad.