Bonjour cher 2N2222,
Various IP adreses are on blacklists of reputation filters, eg due to excessive spam Ă©missions.
Use of Tor, VPN, and other IP relays usually are affected.
Many of my outbound emails bounce as my France fiber IP is shared by 1000s of others, many of whom have malware or Trojan spamming bot infections
One solution is to purchase a static IP adresse and set-up your own servers
Bon Soirée
Jon