Yahoo Received header modification invalidating DKIM signature

From: SM <sm_at_resistor.net>
Date: Tue, 29 Jun 2010 14:58:14 -0700

Hello,

According to Section 6.4 of RFC 5321:

   "The following changes to a message being processed MAY be applied
    when necessary by an originating SMTP server, or one used as the
    target of SMTP as an initial posting (message submission) protocol:

    o Addition of a message-id field when none appears

    o Addition of a date, time, or time zone when none appears

    o Correction of addresses to proper FQDN format"

The first case where a message-id is added hasn't been reported as a
problem. We are aware of problems (third case) when addresses are rewritten.

I haven't come across the second case yet (
http://chilli.nosignal.org/mailman/private/mailop/2010-June/002511.html
) where Yahoo injects the following Received header:

   Received: from [12.157.195.83] by web112620.mail.gq1.yahoo.com via HTTP;
   Tue, 29 Jun 2010 08:01:08 PDT

A timezone is being added:

   Received: from [12.157.195.83] by web112620.mail.gq1.yahoo.com via HTTP;
   Tue, 29 Jun 2010 08:01:08 -0700 (PDT)

Regards,
-sm
Received on Tue Jun 29 2010 - 21:58:49 PST

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