На сервере Centos 6, Postfix, OpenDKIM. Письма на Gmail попадают в спам, вот заголовки:
Received: from u-on.ru (u-on.ru [88.198.49.164]) by mail.u-on.ru (Postfix) with ESMTPA id D20DBD00081 for <ivanskins@gmail.com>; Sun, 14 Sep 2014 19:02:00 +0400 (SAMT)
X-Received: by 10.112.129.228 with SMTP id nz4mr21113038lbb.9.1410706592950; Sun, 14 Sep 2014 07:56:32 -0700 (PDT)
Return-Path: <info@u-on.ru>
Received-Spf: pass (google.com: domain of info@u-on.ru designates 2a01:4f8:131:122b::2 as permitted sender) client-ip=2a01:4f8:131:122b::2;
Authentication-Results: mx.google.com; spf=pass (google.com: domain of info@u-on.ru designates 2a01:4f8:131:122b::2 as permitted sender) smtp.mail=info@u-on.ru; dkim=neutral (no key for signature) header.i=@
Dkim-Signature: v=1; a=rsa-sha256; c=simple/simple; d=u-on.ru; s=default.private; t=1410706920; bh=P9joGKJObSki15Bd60lDp1CHDDzQWerfYCXYmdt9oIA=; h=Message-ID:Date:Subject:From:Reply-To:To:MIME-Version: Content-Type:Content-Transfer-Encoding; b=wRuaRrcXKo9QpmD9HMO098WKepJDa2Qu22TLDBPBKRWCLozTntOwvww6MjmZivFHt A7ceLZ32uaB6rfjJyes3HujgSZ4HK4fbD8B/3mvr2kryg8UyPsJFjDd/LX92VL/W6Q tPBd81QnuTpb+siI9Pg40K6N9GIFA+sCE5pWd5cU=
Message-Id: <1410706920.5415ade8ca375@u-on.ru>
Mime-Version: 1.0
Content-Type: text/html; charset=windows-1251
Content-Transfer-Encoding: quoted-printable
Не удается исправить "dkim=neutral (no key for signature) header.i=@" в Authentication-Results, в чем может быть проблема?