Subject: Undelivered Mail Returned to Sender
From: [email-masked] (Mail Delivery System)
To: [email-masked]
Date: Thu, 20 Sep 2012 12:28:18 +0000 (GMT)

This is the mail system at host mx1.sample.com.

I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. It's attached below.

For further assistance, please send mail to postmaster.

If you do so, please include this problem report. You can
delete your own text from the attached returned message.

                   The mail system

<[email-masked]> (expanded from <[email-masked]>): host
    70.87.28.164[70.87.28.164] said: 550-5.7.1 The message was rejected due to
    classification as Bulk mail. Please see
    http://support.sample.com/email-administrators-guide/error-codes 550
    5.7.1 Please see
    http://support.sample.com/email-administrators-guide/error-codes for
    explanation of the problem. (in reply to end of DATA command)

Subject: foo
From: John Smith <[email-masked]>
To: Fred Bloggs <[email-masked]>
Date: Thu, 20 Sep 2012 13:28:05 +0100

HTML