Political emails that contain more than a short paragraph and a link to the real article always get deleted by yours truly. HTML messages get a stern look before being trashed.

The reason you're sending the email is to alert someone of something, not to offer a 200-page dissertation, and not to decorate their desktop with your beautiful HTML design. So don't include the dissertation or the branding. Something like this:

Subject: Sky falling, Republicans at fault

This is an email to inform you that a new article has been posted on our web site, which we hope illuminates the problems with the specific issue it addresses. Please click the following link to be shown the path to true enlightenment:

http://werule.com/they/suck/

You have received this email because you opted-in. Click this link and follow the instructions to be removed from our mailings:

http://werule.com/opt-out/

Why is that so hard? Could it perhaps be that most of these messages don't actually say anything at all anyway?