Do not remove (possibly invalid) DKIM-Signature headers from outgoing messages

[ykasap]

Sympa removes invalid DKIM-Signature headers from outgoing messages when ARC or DKIM is enabled. Could you please make this behavior optional?

According to section 4.2 of RFC6376,

Signers SHOULD NOT remove any DKIM-Signature header fields from
messages they are signing, even if they know that the signatures
cannot be verified.

A relevant bug report of mailman2:
https://bugs.launchpad.net/mailman/+bug/557493

Expected Behavior

Sympa should not remove existing DKIM-Signature headers from outgoing messages.

Current Behavior

Sympa removes invalid DKIM-Signature headers in Spindle/ProcessOutgoing.pm.

Possible Solution

Do not remove invalid DKIM-Signature headers by default. However, since such a removal might be needed in some circumstances, it can be provided as a configuration option.

Context

I'm a mail system administrator at a university. I need to know which domains are intended to authenticate the message to better understand the DKIM/ARC/DMARC situations of these domains.