Mailing in the Future

As I'm trying to move more VPSs on IPv6-only network, as IPv4 costs money, occasionally my networking dreams smash against some required API reachable only through the old version of the beloved Internet Protocol.

In particular my recurring pain occurs with Scaleway Transactional Emails, which endpoint (integrated by Symfony Mailer Scaleway Bridge) cannot be reached in IPv6. A "feature request" has been opened two years ago, but no feedback has ever been provided...

As today I've resolved this issue for the second time from scratch, I put here some note for future myself.

First of all: NAT64 is a vital resource. You copy the provided IPs in your /etc/resolv.conf file, and the DNS service provides to proxy and masquerade IPv4-only addresses. Most of the work is done just by this.

Then I have to remind to always install the php-curl extension. When this is missing, Symfony Mailer uses the AMPHP implementation which apparently breaks apart trying to connect in IPv4 when an IPv4 address is available and do not tries other options. This also is a quick saving action that I often forget.

As the IPv4 networking is becoming more and more expensive, I really hope to see more services exposing their APIs in IPv6. It is embarassing how, still in 2026, the next version of the Internel Protocol is not only a marginal option, but sometime is not an option at all.