Subject: Undelivered Mail Returned to Sender
From: [email-masked] (Mail Delivery System)
To: [email-masked]
Date: Mon, 1 Mar 2010 12:52:21 +0000 (GMT)

This is the mail system at host server4.example.co.uk.

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]>: host mx01.b.c[194.14.211.245] said: 550
    5.7.1 Message rejected as spam by Content Filtering. (in reply to end of
    DATA command)

Subject: test
From: Customer Services <[email-masked]>
To: Test <[email-masked]>
Date: Mon, 1 Mar 2010 12:51:51 +0000

HTML goes here.