We migrated from CruiseControl to Hudson recently and found that it is not able
to send Rich text email. I checked the Email-Extender plugin but the variables
provided by it are limiting.

So I modified the plugin to use Groovy SimpleTemplate to generate the email
content. A user would set the email content in form of Groovy script through UI.
To the script the build variable would be exposed as a binding

Using that one can extract whatever information he is interested in and then
output it in required form