How can I stop header image from displaying when using send Email tool?

[sperdie]

I am trying to use the Send Mail tool to send an e-mail newsletter in html to subscribers.
I embedded the css into the mail and the formatting looks fine with all formatting exactly how I want, EXCEPT- my mail arrives with the header image from the website on top of the e-mail. Since I am using a smaller version of this image in the actual mail, I now have 2 header images when I send out the mail. The code looks fine by itself- the problem is when a message is sent the system automatically sends with a header image that I do not want. How do I stop this header image from appearing in my outgoing mail? What file controls the formatting of outgoing mail?
I looked over the newsletters.php and mail.php and I am assuming that it is referenced somewhere there but I can't find it.
Thanks

[stevesh]

The HTML email templates are in /email. You want the email_template_newsletters.html