shadowmaster, please update http://www.iredmail.org/forum/post53165.html if you find a solution.

I have same settings, but DKIM signing works for me.

*) There's a global setting in Amavisd config file:

$enable_dkim_signing = 0;          # Disable dkim signing globally.

*) In both $policy_bank{'ORIGINATING'} and $policy_bank{'MYNETS'}, enable DKIM signing like below:

$policy_bank{'ORIGINATING'} = {
    enable_dkim_signing => 1,
    ...
};

This works fine for me.

Could you please turn on debug mode in AMavisd and try again? FYI:
http://www.iredmail.org/docs/debug.amavisd.html

Not FreeBSD. I will give it a try now.

I can reproduce this issue. We must report this issue to FreeBSD port maintainer since Amavisd team didn't release a new version yet.

bartoruiz or shadowmaster,
I found the same problem on Ubuntu 14.04 but I have no idea how to patch the amavisd. Can you help me with this? Thanks.

Zhang,
Thank you for your prompt response. I couldn't find the amavisd file in /usr/sbin/ and /usr/local/sbin/. The only file I thought close to /usr/sbin/amavisd is /usr/sbin/amavisd-new. Then I copied and renamed them into /home/it/amavisd. I also dump the patch into /home/it/amavis-fix.patch. But it failed when I tried to patch:
mx:~$ patch < amavis-fix.patch
patching file amavisd
Hunk #1 FAILED at 34338.
1 out of 1 hunk FAILED -- saving rejects to file amavisd.rej
mx:~$ sudo amavisd-new -h
amavisd-new-2.7.1 (20120429)

I also add whitelisting to amavis. :
mx:~$ tail -n 20 /etc/amavis/conf.d/50-user
# Duplicate or multiple occurrence of a header field
$allowed_header_tests{'multiple'} = 0;

# Missing some headers. e.g. 'Date:'
$allowed_header_tests{'missing'} = 0;

1;  # insure a defined return

# This policy will perform virus checks only.
read_hash(\%whitelist_sender, '/etc/amavis/whitelist');
@whitelist_sender_maps = (\%whitelist_sender);

$interface_policy{'10026'} = 'VIRUSONLY';
$policy_bank{'VIRUSONLY'} = { # mail from the pickup daemon
    bypass_spam_checks_maps   => ['@whitelist_sender_maps'],  # don't spam-check                                                                              this mail
    bypass_banned_checks_maps => ['@whitelist_sender_maps'],  # don't banned-che                                                                             ck this mail
    bypass_header_checks_maps => ['@whitelist_sender_maps'],  # don't header-che                                                                             ck this mail

};

Zhang,
Email from SOGO has DKIM signature but emaisl from mail clients such as: Thunderbird don't have one.
From SOGO:
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=example.com; h= user-agent:message-id:to:mime-version:subject:subject:date:date :content-type:content-type:from:from; s=dkim; t=1482996666; x= 1483860667; bh=T187A03U8q55Kle4eBSo2ObgW6m7xvI8bQ1VV4ITHkc=; b=w a7kVk/LFJO69l2zPhQYqATCGin3bdq7KDm77TkoLAibr+lhhq8kd9mWPEMnb9TVx zjyqwz6JBOBB1FXDahByDmAEtoAPO0zTsebN5fLxF9+XtSJEzfjtKMQ0T2gjx0TL RWQ0xCV4gshxH/7a7y+gw9WFi/rxGAmcLQvmkSeCTM=
The only thing I modified from amavis is whitelisting. Does it affect the dkim signing?
mx:~$ tail -n 20 /etc/amavis/conf.d/50-user
# Duplicate or multiple occurrence of a header field
$allowed_header_tests{'multiple'} = 0;

# Missing some headers. e.g. 'Date:'
$allowed_header_tests{'missing'} = 0;

1;  # insure a defined return

# This policy will perform virus checks only.
read_hash(\%whitelist_sender, '/etc/amavis/whitelist');
@whitelist_sender_maps = (\%whitelist_sender);

$interface_policy{'10026'} = 'VIRUSONLY';
$policy_bank{'VIRUSONLY'} = { # mail from the pickup daemon
    bypass_spam_checks_maps   => ['@whitelist_sender_maps'],  # don't spam-check                                                                              this mail
    bypass_banned_checks_maps => ['@whitelist_sender_maps'],  # don't banned-che                                                                             ck this mail
    bypass_header_checks_maps => ['@whitelist_sender_maps'],  # don't header-che                                                                             ck this mail

};
Edited:
I've commented out the whitelisting mechanism and mail sent from Thunderbird is signed. So my problem is how to whitelist some email accounts from spam check but not affecting the DKIM signing. I will use another thread for my problem. Thanks.

Zhang,
I can achieve the whitelist by modifying ORIGINATING policy bank.
I move the code below before ORIGINATING declaration:
# Load whitelist
read_hash(\%whitelist_sender, '/etc/amavis/whitelist');
@whitelist_sender_maps = (\%whitelist_sender);

I move the code below inside ORIGINATING declaration:
    bypass_spam_checks_maps   => ['@whitelist_sender_maps'],  # don't spam-check this mail
    bypass_banned_checks_maps => ['@whitelist_sender_maps'],  # don't banned-check this mail
    bypass_header_checks_maps => ['@whitelist_sender_maps'],  # don't header-check this mail

Thank you very much for your assistance.

Zhang,
I've removed my VIRUSONLY policy bank so my DKIM signing problem is solved. I moved my whitelisting mechanism to ORIGINATING policy bank. So my new ORIGINATING policy bank becomes like this:
# Load whitelist
read_hash(\%whitelist_sender, '/etc/amavis/whitelist');
@whitelist_sender_maps = (\%whitelist_sender);

# it is up to MTA to re-route mail from authenticated roaming users or
# from internal hosts to a dedicated TCP port (such as 10026) for filtering
$interface_policy{'10026'} = 'ORIGINATING';

$policy_bank{'ORIGINATING'} = {  # mail supposedly originating from our users
    originating => 1,  # declare that mail was submitted by our smtp client
    allow_disclaimers => 1,  # enables disclaimer insertion if available
    enable_dkim_signing => 1,

    # notify administrator of locally originating malware
    virus_admin_maps => ["root\@$mydomain"],
    spam_admin_maps  => [],
    bad_header_admin_maps => [],
    banned_admin_maps => ["root\@$mydomain"],
    warnbadhsender   => 1,
    warnbannedsender => 1,

    # force MTA conversion to 7-bit (e.g. before DKIM signing)
    #smtpd_discard_ehlo_keywords => ['8BITMIME'],

    # don't remove NOTIFY=SUCCESS option
    terminate_dsn_on_notify_success => 0,

    # don't perform spam/virus/header check.
    #bypass_spam_checks_maps => [1],    # spam
    #bypass_header_checks_maps => [1],  # bad header
    #bypass_virus_checks_maps => [1],   # virus
    #bypass_banned_checks_maps => [1],  # banned file names and types

    bypass_banned_checks_maps => ['@whitelist_sender_maps'],  # don't banned-check this mail
};
One cup of coffe served on your table. Xie-xie ni.

Alex Wijoyo