Here's a sample:
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Notification sent to Zen Magnets
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This is a notification that for the transaction 1Y7234300D270613N, we were unable to notify your server at http://zenmagnets.us6.list-manage.com/subscribe/ejunkie-ipn?u=3b1101969991ca7b1b93c864c&id=325c97b513 as we we received the error: HTTP Error 500
POST /subscribe/ejunkie-ipn?u=3b1101969991ca7b1b93c864c&id=325c97b513 HTTP/1.1
Pragma: no-cache
Accept: /
Host: zenmagnets.us6.list-manage.com
Content-type: application/x-www-form-urlencoded
Content-Length: 1464
payment_date=23%3A11%3A22+Feb+26%2C+2014+MST&payer_email=michelle.delgiudice%40gmail.com&address_name=Michelle+DelGiudice&address_state=IL&address_country=United+States&address_city=CHICAGO&address_zip=60657&address_street=3150+North+Lake+Shore+Drive%0A5B&address_country_code=US&address_phone=&first_name=michelle&last_name=delgiudice&payer_id=TPF7YZBZJTD9L&residence_country=US&payer_status=verified&invoice=1lseedxws423kk7550f9erph0cck04kcs4og4o&address_status=Confirmed&payer_business_name=&payer_phone=&custom=&mc_currency=USD&business=payments%40zenmagnets.com&mc_gross=32.98&mc_shipping=0.00&tax=0.00&item_name1=Zen+Booster+Set%3A+216+Zen+Magnets.+6+Spares%2C+.5mm+PVC+Card+and+Velvet+Sack.&item_number1=276195&mc_gross_1=32.98&quantity1=1&num_cart_items=1&pending_reason=None&txn_id=1Y7234300D270613N&payment_status=Completed&txn_type=expresscheckout&payment_type=instant&mc_fee=1.26&mailing_list_status=true&client_id=74894&item_name=Zen+Booster+Set%3A+216+Zen+Magnets.+6+Spares%2C+.5mm+PVC+Card+and+Velvet+Sack.&item_number=276195&quantity=1&option_name1=&option_selection1=&option_name2=&option_selection2=&option_name3=&option_selection3=&charset=utf-8&charset_assumed=true&buyer_ip=216.80.32.180&handshake=258f657977d8e8618ffc748bb9ec830d&discount_codes=&from_name=Zen+Magnets&from_email=contact%40zenmagnets.com&mailing_list_status=true&client_shipping_method_id=43871&shipping_method_type=custom_flat&shipping_method_desc=Cheapest&ej_txn_id=22541633
HTTP/1.1 500 Internal Server Error
Server: nginx
Date: Thu, 27 Feb 2014 06:10:53 GMT
Content-Type: text/html; charset=UTF-8
Content-Length: 4029
Connection: keep-alive
X-UA-Compatible: IE=edge,chrome=1
Set-Cookie: AVESTAENVIRONMENT=prod; path=/
<!DOCTYPE html>
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<meta name="apple-mobile-web-app-capable" content="yes" />
<title>We've Encountered a Problem | MailChimp</title>
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<style type="text/css">
/* Duplicating CSS classes since this page can not load theone.less */
* { -moz-box-sizing: border-box; -webkit-box-sizing: border-box; box-sizing: border-box;}
html, body, div, span, object, iframe,h1, h2, h3, h4, h5, h6, p, blockquote, pre,a, abbr, acronym, address, code,del, dfn, em, img, q, dl, dt, dd, ol, ul, li,fieldset, form, label, legend, textarea,table, caption, tbody, tfoot, thead, tr, th, td {margin: 0;padding: 0;border: 0;font-weight: inherit;font-style: inherit;font-size: 100%;font-family: inherit;vertical-align: baseline;line-height: 1.5em;}
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h1, .h1 {font-size: 2.5em; line-height: 1.2em; margin-bottom: 0.15em;}
h4, .h4 {font-size: 1.125em; font-weight: 500; letter-spacing: 0.01em; line-height: 1.66667em; margin-bottom: 0.333333em;}
p, .p {font-size: 0.9375em;line-height: 1.6em;margin-bottom: 1.2em;max-width: 550px;}
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}
button.p0, .button.p0, .button-small.p0 {background-color: #737373; border: medium none;color: #FFFFFF;}
/* EO Duplicating CSS classes since this page can not load theone.less */
.error-page{ max-width: 390px;}
.error-image{ padding: 56px 0 30px 0; }
</style>
</head>
<body class="error-page bg-white centered">
<!-- 500 image -->
<div class="line error-image">
<div class="lastUnit size1of1 alignc">
<img src="/images/500.png" />
</div>
</div>
<!-- 500 image -->
<!-- 500 message -->
<div class="line below36">
<div class="lastUnit size1of1">
<h1 class="h4">We're sorry</h1>
<p>We're having trouble loading this page. This is either because we can't connect to the database, or we can't find some info on the page you were viewing.</p>
<p>If you need one-on-one help with your MailChimp account, you'll find links to live chat or email with our friendly in-house support team after you <a href="http://kb.mailchimp.com/home" target="blank">search our knowledge base.</a></p>
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</body>
</html>