The mailing list for listmasters using Sympa

[Steve Shipway <address@concealed>]

I'm not sure what possible workarounds there really are.

You cannot just strip the DKIM signature (as Yahoo.com's DMARC record states
the DKIM must be present and correct).

Leaving the Subject, From and Reply-To unmodified does not work, since Yahoo
make their DKIM signature also apply to the Receive headers.  Passing
through your system will always add some of these rendering the signature
invalid.

Stripping the signature AND anonymising the From header works (at least,
where I've tried it here), but this of course removes the identity of the
sender.  This functionality is already present in Sympa (add the
remove-headers and anonymous options to your list) but is not really
desirable.

I cannot see any way to allow the From header to remain unchanged as an
@yahoo.com address, but for the message to still pass DMARC.

One possibility might be to add a new anonymising mode, where the From
address is replaced, but the original is preserved as the Full Name.  EG:

From: Steve Shipway <address@concealed>

...can be rewritten as...

From: "Steve Shipway <address@concealed>" <address@concealed>

This might be a vaguely acceptable solution.  It would require a little work
in Sympa though to add the new option to the system, possibly as a suboption
to anonymous_sender, so only modifying List.pm.  I'll take a look and see if
I can make a suggested patch.

Steve 


Steve Shipway
address@concealed

Attachment: smime.p7s
Description: S/MIME cryptographic signature