Modern internet mail rules and mailing list Subject rewriting

Hi,

Monitoring the mail system, I've found that Google still has us rate
limited. Trying to understand why, I've come up with the following reason:

Google verifies DKIM as part of their criteria for identifying SPAM. We
sign our outgoing mail, so, there shouldn't be a problem. However, some
mail *already* has a DKIM signature. Still no problem, but most mailing
lists change the Subject: line by prepending the mailing list name.

Now *that*'s a problem: it invalidates the pre-existing signature! So,
simply strip the old DKIM headers, you might say. That will make the
problem go away. Well, in fact it probably doesn't: domains which use DKIM
can also state a policy that all mail from the domain should be signed.
Stripping the DKIM signature makes the mail invalid with respect to that
policy, again triggering the SPAM rules.

My conclusion: we have to stop munging the Subject: line in the mailman
mailing lists.

Any comments?

-- 
Bye,

Erik.

http://efficito.com -- Hosted accounting and ERP.
Robust and Flexible. No vendor lock-in.

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