IPv6 only setup - any known issues?

solick

Hi I currently run mailcow on a cloud vm at Hetzner with IPv4 and IPv6 address.

I am planning to migrate to a ipv6 only VM on my proxmox cluster. Are there any known issues running mailcow with a static ipv6 address only?

I was experiencing with other modern applications issues with IPv6 only setups so I would be sure that there are now known issues with that on mailcow.

mlcwuser

Thechnically it should work, practically you will have lots of non-deliverable mail. Or in other words: You will not be able to send / receive emails to / from mail servers that are IPv4 only. And there are more of them than you might think, even in 2022.

solick

Yes that is also my concern. It’s a shame that after such a long time of IPv6 introduction still a lot of services relay on IPv4.

mlcwuser

Yes, and I must admit I am also one of those who has not really dealt with IPv6, yet.. ;-)

Anyways: I wouldn’t go IPv6 only, unless your mail server has a very specific use case where you can say with certainty that it only needs to be able to communicate with IPv6 capable servers / domains.

solick

The reason is that I have setup a proxmox cluster at Hetzner with vSwitch and Ipv6 subnet only because Ipv4 subnet are pretty expensive now. But your hint is valid so I will either buy a small ipv3 subnet or leave the mc instance at the Hetzner cloud by now.