Following the email-ext plugin documentation, I attempted to use the
$CHANGES_SINCE_LAST_SUCCESS token in my custom email message. However, in my
succession of unstable builds, it only returned the changes from the most recent
build.

This is with Hudson 1.300 and email-ext plugin 2.2.1 - the most recent releases
in both cases.

Looking at the Hudson code repository, it looks as though quite a few changes to
the email-ext plugin have been committed in the last few months (including
support for rich text messages?), but not yet released.