Don't send the website owners an email saying that everything it finds infringes on their copyrights.
Don't send the website owners another email telling them that list is a DMCA takedown notice.
Don't bother to vet your request to ensure it only includes works that are infringing on your clients' copyrights.
Don't include a high-quality eZine that chooses to distribute itself online through that website in your list (go back to the list and search for "Ray Gun Revival")
In particular, don't include a Creative Commons-licensed work by a writer who thinks the DMCA is insane on your list because one of those names is mentioned in a cover blurb (go back to the list and search for "Down and Out in the Magic Kingdom").
(And yeah, if you're the service provider or webmaster and you get a "take down notice" don't just take down the stuff before confirming that the request follows the standard for a takedown notice, and if it doesn't ask the person to re-submit a notice that does.)