Amazon SES, understand errors and avoid suspension

I started using Amazon SES to send newsletters (more than 30k emails). I have 2 problems.

Errors

I receive lots of errors like these:

Diagnostic-Code: smtp; 554 4.4.7 Message expired: unable to deliver in 840 minutes.<421 4.4.0 Unable to lookup DNS for DOMAIN.it>
Diagnostic-Code: smtp; 554 4.4.7 Message expired: unable to deliver in 840 minutes.<421 <CASELLA@alice.it> Service not available - too busy>
Diagnostic-Code: smtp; 554 4.4.7 Message expired: unable to deliver in 840 minutes.<421 4.4.1 Failed to establish connection>
Diagnostic-Code: smtp; 554 4.4.7 Message expired: unable to deliver in 840 minutes.<421 4.4.2 Connection timed out>
Diagnostic-Code: smtp; 550 4.4.7 Message expired: unable to deliver in 840 minutes.<421 4.4.2 Connection closed unexpectedly>
Diagnostic-Code: smtp; 554 4.4.7 Message expired: unable to deliver in 840 minutes.<421 4.4.0 Unable to lookup DNS for ANOTHERDOMAIN.191.it>

Especially this error:

Diagnostic-Code: smtp; 554 4.4.7 Message expired: unable to deliver in 840 minutes.<421 4.4.0 Unable to lookup DNS for sitedomain.it>

I've replaced the domains to protect privacy, but errors refer to different domains.

To see them, I have "return-path". Before using Amazon, I was using a private SMTP and I didn't ever receive those messages.

It seems like lots of addresses are wrong or inexistent, but why I didn't get them before?

What's the explanation?

High Spamassassin Score

I used this tool: http://ift.tt/qS6KUI to check the quality of emails sent and the score is always between 3 and 5.

My emails are only HTML and contain only links to my commercial website. They are news,offers or similar things for my clients (they opted in the newsletter).

I have DKIM enabled for the domain.

How can I produce a better HTML to lower the spamassasin score and avoid spam?

This is the full message including full headers and content:

Content-Filter: maildrop-toaster
Return-Path: <0000014c703b095b-d06c5ff8-cabd-409e-96ed-187a8a98157e-000000@eu-west-1.amazonses.com>
Delivered-To: clientdomain.it-info@clientdomain.it
Return-Path: <0000014c703b095b-d06c5ff8-cabd-409e-96ed-187a8a98157e-000000@eu-west-1.amazonses.com>
X-Spam-Flag: YES
X-Spam-Checker-Version: SpamAssassin 3.2.5 (2008-06-10) on mail3.clientdomain.it
X-Spam-Level: **************************************************
X-Spam-Status: Yes, score=50.1 required=5.0 tests=AWL,DNS_FROM_AHBL_RHSBL,
    HTML_IMAGE_RATIO_04,HTML_MESSAGE,MIME_HTML_ONLY,OROLOGIO1,RDNS_NONE
    autolearn=disabled version=3.2.5
X-Spam-Report: 
    *  2.0 DNS_FROM_AHBL_RHSBL RBL: Envelope sender listed in dnsbl.ahbl.org
    *   50 OROLOGIO1 URI: OROLOGIO1
    *  0.2 HTML_IMAGE_RATIO_04 BODY: HTML has a low ratio of text to image area
    *  0.0 HTML_MESSAGE BODY: HTML included in message
    *  1.7 MIME_HTML_ONLY BODY: Message only has text/html MIME parts
    *  0.1 RDNS_NONE Delivered to trusted network by a host with no rDNS
    * -3.9 AWL AWL: From: address is in the auto white-list
Delivered-To: clientdomain.it-info@clientdomain.it
Received: (qmail 24091 invoked by uid 89); 31 Mar 2015 14:34:55 -0000
Received: by simscan 1.4.0 ppid: 24076, pid: 24088, t: 0.0709s
         scanners:none
Received: from unknown (HELO a6-10.smtp-out.eu-west-1.amazonses.com) (54.240.6.10)
  by mail3.clientdomain.it with SMTP; 31 Mar 2015 14:34:55 -0000
DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/simple;
    s=uku4taia5b5tsbglxyj6zym32efj7xqv; d=amazonses.com; t=1427812059;
    h=Date:From:To:Message-Id:Subject:Mime-Version:Content-Type:Feedback-ID;
    bh=5bGosed0XiWcFgHNXhhXU4e1wN6LXAXi91I3/eH9smI=;
    b=YA3ERPB8ZTKHSwT8GdA9o2cFZlvNLhiOSPTDjAXS8k6CegLLOWyRAKlZF3So6CSW
    rVLUgkYcCVn/Mi7+Ds2afv8uonP93Quh7rTmVjz4JU7dm3HbiUQd3J8ApDqwz2fZ5y0
    uCOba0L88jzsiWJJraMnbP/zM+IHUpLusbHd+U1s=
Date: Tue, 31 Mar 2015 14:27:39 +0000
From: mydomain Italia <mydomain.italia@mydomain.it>
To: info@clientdomain.it
Message-ID: <0000014c703b095b-d06c5ff8-cabd-409e-96ed-187a8a98157e-000000@eu-west-1.amazonses.com>
Subject: ***SPAM*** Eventi mydomain Italia 2015 
Mime-Version: 1.0
Content-Type: text/html; charset=utf-8
X-SES-Outgoing: 2015.03.31-54.240.6.10
Feedback-ID: 1.eu-west-1.z7yglAL5GywH6H26FcViauiBZKVY/EL6nMHx51tLzEY=:AmazonSES
X-Spam-Prev-Subject: Eventi mydomain Italia al  2015 

<html>
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    <title>Newsletter</title>
  <style type="text/css">
    body { font: normal 13px Verdana; width: 800px; }
    #footer {
      background: #DCE4FD;
      padding: 10px;
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<!--          /* Client-specific Styles */          #outlook a {padding:0;} /* Force Outlook to provide a "view in browser" menu link. */          body{width:100% !important; -webkit-text-size-adjust:100%; -ms-text-size-adjust:100%; margin:0; padding:0;}          /* Prevent Webkit and Windows Mobile platforms from changing default font sizes, while not breaking desktop design. */          .ExternalClass {width:100%;} /* Force Hotmail to display emails at full width */          .ExternalClass, .ExternalClass p, .ExternalClass span, .ExternalClass font, .ExternalClass td, .ExternalClass div {line-height: 100%;} /* Force Hotmail to display normal line spacing.  More on that: http://ift.tt/A8lgfa */          #backgroundTable {margin:0; padding:0; width:100% !important; line-height: 100% !important;}          img {outline:none; text-decoration:none;border:none; -ms-interpolation-mode: bicubic;}          a img {border:none;}          .image_fix {display:block;}          p {margin: 0px 0px !important;}                    table td {border-collapse: collapse;}          table { border-collapse:collapse; mso-table-lspace:0pt; mso-table-rspace:0pt; }          /*a {color: #e95353;text-decoration: none;text-decoration:none!important;}*/          /*STYLES*/          table[class=full] { width: 100%; clear: both; }                    /*################################################*/          /*IPAD STYLES*/          /*################################################*/          @media only screen and (max-width: 640px) {          a[href^="tel"], a[href^="sms"] {          text-decoration: none;          color: #ffffff; /* or whatever your want */          pointer-events: none;          cursor: default;          }          .mobile_link a[href^="tel"], .mobile_link a[href^="sms"] {          text-decoration: default;          color: #ffffff !important;          pointer-events: auto;          cursor: default;          }          table[class=devicewidth] {width: 440px!important;text-align:center!important;}          table[class=devicewidthinner] {width: 420px!important;text-align:center!important;}          table[class="sthide"]{display: none!important;}          img[class="bigimage"]{width: 420px!important;height:219px!important;}          img[class="col2img"]{width: 420px!important;height:258px!important;}          img[class="image-banner"]{width: 440px!important;height:106px!important;}          td[class="menu"]{text-align:center !important; padding: 0 0 10px 0 !important;}          td[class="logo"]{padding:10px 0 5px 0!important;margin: 0 auto !important;}          img[class="logo"]{padding:0!important;margin: 0 auto !important;}           }          /*##############################################*/          /*IPHONE STYLES*/          /*##############################################*/          @media only screen and (max-width: 480px) {          a[href^="tel"], a[href^="sms"] {          text-decoration: none;          color: #ffffff; /* or whatever your want */          pointer-events: none;          cursor: default;          }          .mobile_link a[href^="tel"], .mobile_link a[href^="sms"] {          text-decoration: default;          color: #ffffff !important;           pointer-events: auto;          cursor: default;          }          table[class=devicewidth] {width: 280px!important;text-align:center!important;}          table[class=devicewidthinner] {width: 260px!important;text-align:center!important;}          table[class="sthide"]{display: none!important;}          img[class="bigimage"]{width: 260px!important;height:136px!important;}          img[class="col2img"]{width: 260px!important;height:160px!important;}          img[class="image-banner"]{width: 280px!important;height:68px!important;}                    }        -->
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<td style="font-family: Helvetica, arial, sans-serif; font-size: 10px; color: #999999;" align="right" valign="middle"><a href='http://ift.tt/1EJcUZE' target="_blank"></a>i</td>
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<td class="logo" style="padding: 10px 0 10px 20px;" width="270" valign="middle">
<div><a href="http://www.mydomain.it" target="_blank"><img style="float: left; border: 1px #f6f4f5;" src="http://bit.ly/logomydomain" alt="" width="233" height="107" /></a></div>
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<td align="center"><a href='http://ift.tt/1EJcUZG' target="_self" title=" 2015"><img style="border: 1px solid white;" src="http://ift.tt/1Cdiblh" alt="" width="541" height="299" /></a></td>
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<td style="font-family: Helvetica, arial, sans-serif; font-size: 18px; color: #333333; text-align: left; line-height: 20px;">Fiera di Roma 8-10 aprile 2015<br /></td>
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<td style="font-family: Helvetica, arial, sans-serif; font-size: 13px; color: #95a5a6; text-align: left; line-height: 24px;">
<p><strong>mydomain Italia &egrave; lieta di invitarLa ai due seguenti incontri</strong><em> </em></p>
<p><strong>9 aprile ore 16.00</strong> <em>- "Il distributore 2.0 e il ruolo degli installatori" &egrave; rivolto  ad installatori, operatori del settore. Introduzione e moderazione a cura di Maurizio.<br /></em></p>
<p><strong>10 aprile ore 10.00</strong> -<em> "Industria e retail: la diagnosi energetica quale elemento chiave per la  competitivit&agrave;" &egrave; rivolto ad industrie, retail, grande distribuzione organizzata, energy manager.</em></p>
<p><strong>Richiedi i biglietti omaggio al tuo referente commerciale</strong><em><br /></em></p>
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<td style="font-family: Helvetica, arial, sans-serif; font-size: 10px; color: #999999;" align="center" valign="middle">Se non desideri pi&ugrave; ricevere quetsa mail <a href="http://ift.tt/1EJcTFf">clicca qui</a><br /></td>
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