Jenkins email-ext plugin thinks I have no recipients configured

For those using this plugin in combination with Job DSL. I have do add the sendTo { recipientList() } block explicitly to the different triggers.

So my DSL looked like this:

extendedEmail {
    recipientList('${EMAIL_RECIPIENTS}')
    triggers {
        failure {
            subject('The subject')
            content("The content")
            sendTo {
                recipientList()
            }
        }
    }
}

Turns out plugin configuration is somewhat non-intuitive; a necessary setting is buried behind an Advanced button. I got answers in https://issues.jenkins-ci.org/browse/JENKINS-34731 and it is working now as follows:

In the Advanced settings, Triggers -> Failure - Any lists "Developers" by default, but not "Recipient List."