2026-03 regression that breaks reverse-proxy setups

[schuay]

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Description

Filing a new bug so the report in #7114 isn't lost. PTAL there. This is an urgent issue, and the other bug is incorrectly filed as not planned.

Steps to reproduce:

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Logs:

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Which branch are you using?

master (stable)

Which architecture are you using?

x86_64

Operating System:

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Server/VM specifications:

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Is Apparmor, SELinux or similar active?

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Virtualization technology:

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Docker version:

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docker-compose version or docker compose version:

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mailcow version:

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Reverse proxy:

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Logs of git diff:

Logs of iptables -L -vn:

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Logs of ip6tables -L -vn:

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Logs of iptables -L -vn -t nat:

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Logs of ip6tables -L -vn -t nat:

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DNS check:

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