Double X-DKIM Header (all the way across the sky!!!!)

From: Steve Jenkins <stevejenkins_at_gmail.com>
Date: Mon, 14 Feb 2011 18:27:35 -0800

I just added Amavis-new (with ClamAV and SpamAssassin) to my Postfix
setup on my personal box.

For context, I'm using this content_filter argument in Postfix to push
incoming mail through the filter on port 10024:

content_filter = smtp-amavis:[127.0.0.1]:10024

Then I've added the following to /etc/postfix/master.cf to set up port
10025 for the mail to be re-injected into the Postfix queue:

smtp-amavis unix - - n - 2 smtp
    -o smtp_data_done_timeout=1200
    -o smtp_send_xforward_command=yes
    -o disable_dns_lookups=yes
    -o max_use=20

127.0.0.1:10025 inet n - n - - smtpd
    -o content_filter=
    -o local_recipient_maps=
    -o relay_recipient_maps=
    -o smtpd_restriction_classes=
    -o smtpd_delay_reject=no
    -o smtpd_client_restrictions=permit_mynetworks,reject
    -o smtpd_helo_restrictions=
    -o smtpd_sender_restrictions=
    -o smtpd_recipient_restrictions=permit_mynetworks,reject
    -o smtpd_data_restrictions=reject_unauth_pipelining
    -o smtpd_end_of_data_restrictions=
    -o mynetworks=127.0.0.0/8
    -o smtpd_error_sleep_time=0
    -o smtpd_soft_error_limit=1001
    -o smtpd_hard_error_limit=1000
    -o smtpd_client_connection_count_limit=0
    -o smtpd_client_connection_rate_limit=0
    -o receive_override_options=no_header_body_checks,no_unknown_recipient_checks

Now, when I sent a test message from my GMail account to my personal
server to check that Amavis-new is working correctly, I noticed that
I'm getting two X-DKIM headers, as follows:

X-DKIM: OpenDKIM Filter v2.3.0 carbonfiber.stevejenkins.com 830E110424E7
Authentication-Results: carbonfiber.stevejenkins.com; dkim=pass
        (1024-bit key) header.i=_at_gmail.com header.b=IiKEGPTz; dkim-adsp=pass
X-DKIM: OpenDKIM Filter v2.3.0 carbonfiber.stevejenkins.com D120510424E8

I'm assuming one is added on the way IN to the content filter, and the
second is added when Amavis-new re-injects the message back into the
Postfix queue.

I don't see any harm in this, but I don't know if this is a bug or if
it's the desired behavior for some reason. If it's not a bug, any
guidance on how to configure OpenDKIM to parse the message once,
instead of twice?

Thanks,

SteveJ
Received on Tue Feb 15 2011 - 02:27:48 PST

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