It is really frustrating when your email comes through as spam

Spam detection software, running on the system <<yourserver.name.here>>, has
identified this incoming email as possible spam.  The original message
has been attached to this so you can view it (if it isn't spam) or label
similar future email.  If you have any questions, see
the administrator of that system for details.

Content preview:  Dear valued customer, Your order # 100000009 has been Canceled.
  You can check the status of your order by logging into your account.
 [...]

Content analysis details:   (6.7 points, 5.0 required)

 pts rule name              description
---- ---------------------- --------------------------------------------------
 2.4 HTML_IMAGE_ONLY_20     BODY: HTML: images with 1600-2000 bytes of words
 0.0 HTML_MESSAGE           BODY: HTML included in message
 2.3 MIME_HTML_ONLY         BODY: Message only has text/html MIME parts
 1.7 HTML_MIME_NO_HTML_TAG  HTML-only message, but there is no HTML tag
 0.3 HTML_SHORT_LINK_IMG_3  HTML is very short with a linked image
 0.1 RDNS_NONE              Delivered to trusted network by a host with no rDNS
-0.0 AWL                    AWL: From: address is in the auto white-list

The original message was not completely plain text, and may be unsafe to
open with some email clients; in particular, it may contain a virus,
or confirm that your address can receive spam.  If you wish to view
it, it may be safer to save it to a file and open it with an editor.

This was pretty frustrating. So I first created a small Model override that added some proper content to the email so it would not be flagged.

This did not get the results wanted the message was still flagged. I ended up changing a core file.

You can grab the module here; it is donationware; depending on the results, we may release more in this manor.

http://www.collinsharper.com/index.php/magento-email-spam-fix.html

Let me know how it works out for you.