Domain wide footer with <p- changes content type to text/html

[support3pc]

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Description

OK I got a weird one when fowarding the following E-Mail with global footer enabled it transforms both content-types of the multipart/alternative to text/html.

final.eml

Which then shows the text/html without linebreaks. This happens because the first part is a plain text part in disguise (plain text without <br> or <p>) and does not show the line breaks.

The "&lt;p-" symbol happens when e-mails get forwarded and an e-mail beginns with "p-" they are often shown in "<>"-brackets and together they can show up as "<p-1334@domain.de>" or "&lt;p-1334@domain.de&gt;".

This only occurs with at least 4 of these symbols ("&lt;p-"). This only occurs with domain wide footers enabled.

Steps to reproduce:

1. Enable domain wide footers.
2. Forward the attached e-mail.
3. Look at the content type of both multipart/alternatives (both should be text/html).

final.eml

Logs:

not important

Which branch are you using?

master (stable)

Which architecture are you using?

x86_64

Operating System:

Debian GNU/Linux 11 (bullseye)

Server/VM specifications:

not important

Is Apparmor, SELinux or similar active?

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Virtualization technology:

not important

Docker version:

not important

docker-compose version or docker compose version:

not important

mailcow version:

2025-09b

Reverse proxy:

not important

Logs of git diff:

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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:

not important