The built-in email notification works. This log snippet is with both enabled.

Build did not succeed and the project is configured to only push after a successful build, so no pushing will occur.
Sending e-mails to: cnelson@******.com
Email was triggered for: Failure - Any
Sending email for trigger: Failure - Any
An attempt to send an e-mail to empty list of recipients, ignored.

Please enable debug mode for email-ext in the manage Jenkins area. There is a check box there for it. Then rerun the job and post the log.

Thanks, Alex. The only log related to the job is

<my project name> #9 main build action completed: FAILURE

Please check that you enabled debug mode in the "Configure System" area under the Extended Email Publisher. Can you verify that "Recipient List" is setup in the Failure trigger in the Advanced area in the job itself?

In the Advanced settings, Triggers -> Failure - Any listed "Developers" but not "Recipient List." When I add Recipient List my console output says:

Checking if email needs to be generated
Email was triggered for: Failure - Any
Sending email for trigger: Failure - Any
messageContentType = text/plain; charset=UTF-8
Adding recipients from project recipient list
Adding recipients from trigger recipient list
Setting In-Reply-To since last build was not successful
Successfully created MimeMessage
Sending email to: <me>

If not including the recipient list is the default, that's not very helpful. I would not have expected to have to open Advanced settings to get basic functionality.

A separate issue, I'm sure, but $BUILD_URL doesn't seem to include a protocol. The only reason I am using this plugin instead of the built-in functionality is so that my notification has a clickable link to the job. I guess I at least gain the ability to put "http://$BUILD_URL" in the body but it's odd that the URL is incomplete.

Not including the recipient list by default for failures is a historical issue. It was that way for a long time and when I tried enabling recipient list for Failures, people were upset that the behavior changed.

For BUILD_URL, it takes it from the following: jenkins.getRootUrl() + build.getUrl(), check your URL setting in the Manage Jenkins area under "Jenkins Location Configuration"