Using the XslTransform pipeline component is a simple way to send HTML formatted email from BizTalk, but specifying the style sheet at design time means keeping track of the full path to the XSL file.
To make life easier, I deploy style sheets to the Pipeline Components directory and use a pre-build script to copy the XSL file so it’s available at build-time.
copy /y “$(ProjectDir)\StyleSheet.xsl” “%BTSINSTALLPATH%\Pipeline Components”
Bear in mind this will overwrite the runtime’s style sheet every time you build, so it’s not good for environments where you’re developing on a test or production box. If you’re not using source control, you could lose your style sheet in a click-stance!
There are more robust ways to do this, I’m sure, and I leave it to the readers to safeguard their work.