The documentation for email-ext states:
The input labeled Default Recipients can be used to set a default list of email addresses for all projects using plugin (it can be overridden at the project level). This can be used to greatly simplify the configuration you need to do for all projects.
This is great, except that the Default Recipients list does not appear in my global settings for Jenkins. Viewing source shows that it is not present at all, not merely hidden. Maybe I just don't see where it's supposed to go, or maybe the documentation is just inaccurate?