The PTR check reported a correctly published record as wrong. The lookups
went through the container's resolver (127.0.0.11) which forwards to the
host's systemd-resolved, and systemd-resolved synthesises the reverse
lookup of the machine's own addresses from the local hostname rather than
asking public DNS. On the production host that meant
203.0.113.10 -> provider-assigned-hostname (does not match)
while public DNS has had 203.0.113.10 -> selfpost.example.com all along.
These checks exist to report what a receiving mail server sees, so they
now dial recursive resolvers themselves, defaulting to 1.1.1.1, 8.8.8.8
and 9.9.9.9 and overridable with SELFPOST_DNS_RESOLVERS. The e2e stand
sets it to its CoreDNS, which the `dns:` directive alone no longer covers.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
mix
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