How to use Hudson "Parameterized Build" values in an email

You need to use a parameter like this one: ${ENV, var="USER"}

And 'USER' is the same as 'user' - you need to give then different names.

On top of what Rene suggests (that is, to use ${ENV, var="USER"}) I believe you need to install yet another plugin called 'email-ext'. I found that information in some other question (there's no accepted answer though).