Hello. I got several dedicated servers on OVH with failover IPs for VPS KVM. Most of IPV4 IP ranges are with good reputation. But lately I bought several single failover IPS and small ranges... and most of them are in OUTLOOK blacklist bouncing email. My email settings score is 10/10 (DKIM, SPF, DMARC)... everything OK. So i stucked because OVH cannot provide me more single IPs with 100% good reputation (Microsoft added most of their IP ranges to blocklist and dont want to remove)... so OVH technician told me that solution is to send emails via IPV6 IP. So my question is: 1) what are your experiences and are there any contraindications to send emails via IPV6? most of topics here are how to disable IPV6 in postfix 2) how to setup POSTFIX to send emails only via IPV6. For this setup I can build VPS from scratch that is why i dont give any information about system (mostly Debian 9/10)... Waiting for Your kindly reply. Maciej p.s. Why I need single failover IPs? because some servers/clients need to be scalable and fast migrate to different server scenarios... single failover can be moved between servers without any problems within minutes... those IPs with good reputation are in 12/24 ranges and all must be moved. It is also good to have failover for disaster recovery scenarios... that is why i am trying to solve this issue.