That is not related to certificates/TLS/Let's Encrypt. I'm talking about the confusing name and contents of your certificates as seen in the certbot output.
Anyway, a few issues:
- Your IMAP and SMTP services are still using the expired certificate, probably because they are refering to the certificate named
hygiene-bucco-dentaire.comwith the file/etc/letsencrypt/live/hygiene-bucco-dentaire.com/fullchain.pem. That is not the same certificate you issued in your pastebin output, because that certificate is calledmail.conceptys-france.combut with the single hostnameconceptys-france.comin it. - That new certificate wasn't installed in nginx, because nginx isn't properly configured, so certbot doesn't understand its configuration file.