I'm struggling with the same issue, but I've narrowed the problem down to Outlook 2007, which uses Word 12 to display HTML email. Microsoft has acknowledged that it's broken but will not be fixing it. This has been confirmed by other HTML mail developers who sent over 20,000 emails to Microsoft about it. Outlook 2003, Mac Mail, GMail and Yahoo mail all work perfectly. I'll continue testing today with some CC templates instead of custom code.
... View more