While I ignore puppet 4's brain-dead stupid fact behaviour when using puppetdb, I'm on to the issue of getting puppet to mail reports when something changes on a node.
Since the built-in tagmail is no longer an option, I decided to look at the tagmail module. As far as I can tell, the puppetlabs-tagmail module can NOT be used with puppet 4.1.
tagmail requires 'tagmap' to be set in puppet.conf, but 'tagmap' is not one of the core configuration items, and puppet 4.1 does not allow extensions to add config options, so puppet ignores the 'tagmap' setting and tagmail errors out when it attempts to process the report.