Thanks I downloaded it but in the instruction for installation it says
## Installation
1. Copy Stylesheet to Settings => General => Email => Stylesheet
2. Copy header.tpl content to Settings => General => Email => Header
3. Coy footer.tpl content to Settings => General => Email => footer
4. Edit every message and replace its content with all the various *.tpl file's content.
I have no idea what it means. I do not have in my whmcs settings general email styleheet ?