Hm, we already had that file in our repository before we upgraded to 1.509.4 from 1.509.2. And given that emailext 2.35.1 requires 1.509.4 it should be possible to use that file. Or do I miss something?

https://github.com/mozilla/mozmill-ci/blob/master/jenkins-master/jenkins.model.JenkinsLocationConfiguration.xml