Why does OpenDKIM sign the email twice?

Question

linux

I have ubuntu server 12.04 with iRedMail mailer.
Set up Postfix + Opendkim according to this article habrahabr.ru/post/151904
As a result, the letter is signed twice. And that's why it doesn't pass the test. What could be causing this?

Received: by mail-tester.com (Postfix, from userid 500)	id 007291C8263;
  Thu, 12 Jun 2014 15:19:32 +0200 (CEST)
X-Spam-Checker-Version: SpamAssassin 3.3.2 (2011-06-06) on mail-tester.com
X-Spam-Flag: YES
X-Spam-Level: *******
X-Spam-Report: *  1.6 SUBJ_ALL_CAPS Subject is all capitals
  *  0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily
  *      valid
  *  1.7 URIBL_DBL_SPAM Contains an URL listed in the DBL blocklist
  *      [URIs: windfx.ru]
  *  1.8 URIBL_BLACK Contains an URL listed in the URIBL blacklist
  *      [URIs: windfx.ru]
  *  0.6 URIBL_SBL Contains an URL's NS IP listed in the SBL blocklist
  *      [URIs: windfx.ru]
  *  1.3 RDNS_NONE Delivered to internal network by a host with no rDNS
  *  0.0 T_DKIM_INVALID DKIM-Signature header exists but is not valid
  *  0.2 BODY_URI_ONLY Message body is only a URI in one line of text or for
  *      an image
X-Spam-Status: Yes/7.4/5.0
X-Spam-Test-Scores: BODY_URI_ONLY=0.249,DKIM_SIGNED=0.1,RDNS_NONE=1.274,
  SUBJ_ALL_CAPS=1.625,T_DKIM_INVALID=0.01,URIBL_BLACK=1.775,URIBL_DBL_SPAM=1.7,
  URIBL_SBL=0.644
X-Spam-Last-External-IP: 193.104.225.2
X-Spam-Last-External-HELO: mx.to-text.ru
X-Spam-Last-External-RDNS: 
X-Spam-Date-of-Scan: Thu, 12 Jun 2014 15:19:32 +0200
Received: from mx.to-text.ru (unknown [193.104.225.2])
  by mail-tester.com (Postfix) with ESMTPS id 79B5C1C80AF
  for <[email protected]>; Thu, 12 Jun 2014 15:19:31 +0200 (CEST)
Received: from localhost (localhost [127.0.0.1])	by mx.to-text.ru (Postfix)
  with ESMTP id 9DCCC854CB	for <[email protected]>;
  Thu, 12 Jun 2014 20:22:21 +0700 (NOVT)
X-DKIM: OpenDKIM Filter v2.6.8 mx.to-text.ru 9DCCC854CB
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=windfx.ru; s=mail;
  t=1402579341; bh=hOHjfRXjq/yS0BrFkISPE46ojsV3bhe3yej7EWOPj9I=;
  h=Date:From:To:Subject;
  b=bUivoPJy1qbqYn8snuN4/gt2jSJH/fI4oFMVNyPZV357jey/3YJXY8P995dnpV3yD
  RA1+UfvbshklEe8EZHMt2u8wKBJyfpNyHservUCAHG73XXdy8GgT3nW0TkXDwVNuoX
  OOEZrrY6Fbf8YFB4cIDpiHI5W8Xnn8aLE/YmINOU=
X-Virus-Scanned: Debian amavisd-new at mx.to-text.ru
Received: from mx.to-text.ru ([127.0.0.1])
  by localhost (mx.to-text.ru [127.0.0.1]) (amavisd-new, port 10024)
  with ESMTP id 9o0Uf4iAlO8L for <[email protected]>;
  Thu, 12 Jun 2014 20:22:17 +0700 (NOVT)
Received: from to-text.ru (localhost [127.0.0.1])	by mx.to-text.ru (Postfix)
  with ESMTPA id F35A3853FF	for <[email protected]>;
  Thu, 12 Jun 2014 20:22:15 +0700 (NOVT)
X-DKIM: OpenDKIM Filter v2.6.8 mx.to-text.ru F35A3853FF
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=windfx.ru; s=mail;
  t=1402579337; bh=hOHjfRXjq/yS0BrFkISPE46ojsV3bhe3yej7EWOPj9I=;
  h=Date:From:To:Subject;
  b=PUYubls/Uhr3y4kc8MrGdp5zW4QQT4URmToDvGJFVtqgroUB78BEWVrChbjynqH6F
  37mYiEXUPS6gJ0DHXJxfTcSVkClaLDauNjzO/nXGpYlBSXNjchceXBxXH0+QWucomi
  GeDmwC85o91xOtGzFPORV++LtxF41R4g9XKR/dJ0=
Date: Thu, 12 Jun 2014 20:22:15 +0700
From: [email protected]
To: [email protected]
Subject: =?UTF-8?Q?=D0=9F=D1=80=D0=BE=D0=B2=D0=B5=D1=80=D0=BA=D0=B0=20?=
 =?UTF-8?Q?=D0=BF=D0=BE=D0=B4=D0=BF=D0=B8=D1=81=D0=B8=20DKIM?=
Message-ID: <[email protected]>
X-Sender: [email protected]
User-Agent: RoundCube Webmail
Return-Path: [email protected]
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: quoted-printable

=D0=9F=D1=80=D0=BE=D0=B2=D0=B5=D1=80=D0=BA=D0=B0