Outgoing mail is ending up in spam

Question

I have a problem with all the mails sent from my company, often ending up in the recipients spam folder. It's from approximately 5-6 different mail adresses sending from the same mail server. We have a dedicated server that is both hosting out website aswell as managing all mails and so forth. We usually don't get any error messages when the mails either never arrives, or ends up in the recipients spam folder.

But we received this 1 error message, so i hope you have an idea of what to do to keep our mails out of the spam folders. We might have to hire external developers to take care of the problem, i just want to get an idea of what the problem is, so i know if i can fix it, or tell the developers what to do.

"ANON" is put in, to keep mails involved anonymous. Should i delete anything else?

Error message:

-----Oprindelig meddelelse-----
Fra: Mail Delivery Subsystem [mailto:mailer-daemon@googlemail.com]
Sendt: 27. september 2013 08:26
Til: support@example.com
Emne: Delivery Status Notification (Failure)

Delivery to the following recipient failed permanently:

     ANON@ANON.dk

Technical details of permanent failure: 
Message rejected by Google Groups. Please visit
http://mail.google.com/support/bin/answer.py?hl=en&answer=188131 to review our Bulk Email Senders Guidelines.

----- Original message -----

X-Received: by 10.14.109.66 with SMTP id r42mr7804640eeg.43.1380263171652;
        Thu, 26 Sep 2013 23:26:11 -0700 (PDT)
Return-Path: <support@example.com>
Received: from server.example.com ([2a01:4f8:121:267::2])
        by mx.google.com with ESMTPS id
o7si4443732eep.48.1969.12.31.16.00.00
        (version=TLSv1 cipher=RC4-SHA bits=128/128);
        Thu, 26 Sep 2013 23:26:11 -0700 (PDT)
Received-SPF: neutral (google.com: 2a01:4f8:121:267::2 is neither permitted nor denied by best guess record for domain of support@example.com) client-ip=2a01:4f8:121:267::2;
Authentication-Results: mx.google.com;
       spf=neutral (google.com: 2a01:4f8:121:267::2 is neither permitted nor denied by best guess record for domain of support@example.com) smtp.mail=support@example.com;
       dkim=neutral (bad format) header.i=@example.com
DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=example.com; s=default;

h=Content-Type:MIME-Version:Message-ID:Date:Subject:In-Reply-To:References:T
o:From; bh=E5v2ubiy1T/bYA8pEndEZlZwb928MRpgJuoPSy8WsQE=;

b=AbAc/65Y88xmhdGHxUUs3kK/1rOvTH0uEpPAVEN1sv8KNdJvzvRqiO72gqXan0M7wXRVeev6IJ
0iumBwj875irmYAaST9hzm+eIF02whaZDgkzRr2jjJKN9bn11tBmtlTK0JzTGDUMf1Ij+qmI
0iumBwj875irmYAaST9hzm+eIF02whaZDgkzRr2jjJKN9bn11tBmtlTK0JzTGDUMf1Ij+vdF
0iumBwj875irmYAaST9hzm+eIF02whaZDgkzRr2jjJKN9bn11tBmtlTK0JzTGDUMf1Ij+f
64lUpYIyyaqlNUYnaPt28=;
Received: from post.ABCDEFGHIJK.com ([xxx.xxx.xxx.xxx]:49696
helo=WIN7UVQT1EBIRO)
    by server.example.com with esmtpa (Exim 4.80.1)
    (envelope-from <support@example.com>)
    id 1VPRUi-0008Dh-Os
    for ANON@ANON.dk; Fri, 27 Sep 2013 06:25:41 +0000
From: "ANON - example.com" <support@example.com>
To: "'XYZ ABC'" <a.bcd@efg.hi>
References: <E1VORD0-0007hu-Jn@server.example.com>
<CACyHzxudCSh+4NOEu-_QR1yQYA=uR0DOrTTcgDsg9KcRLTWDFQ@mail.gmail.com>
In-Reply-To:
<CACyHzxudCSh+4NOEu-_QR1yQYA=uR0DOrTTcgDsg9KcRLTWDFQ@mail.gmail.com>
Subject: SV: example.com: Ordre # 700003820 opdatering
Date: Fri, 27 Sep 2013 08:25:38 +0200
Message-ID: <00d501cebb4a$637159b0$2a540d10$@example.com>
MIME-Version: 1.0
Content-Type: multipart/related;
    boundary="----=_NextPart_000_00D6_01CEBB5B.26FF0BB0"
X-Mailer: Microsoft Outlook 14.0
Thread-Index: AQGYr839QgwXgZ5pAdux+XF0Yh5W4AHfGYRhmjY70GA=
Content-Language: da
X-AntiAbuse: This header was added to track abuse, please include it with any abuse report
X-AntiAbuse: Primary Hostname - server.example.com
X-AntiAbuse: Original Domain - ANON.dk
X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12]
X-AntiAbuse: Sender Address Domain - example.com
X-Get-Message-Sender-Via: server.example.com: authenticated_id:
support@example.com
X-Source: 
X-Source-Args: 
X-Source-Dir: 

Answer 1

I needed to edit the MX records for the domains sending the mails, as the domains and websites were on the same server the mail server couldn't comprehend it.