What configures Drupal to send emails on the create or update of an unpublished content? My Drupal installation attempts to send emails to a number of users whenever I create or update content but do not publish it. But because sending email is not configured errors are generated.

I don't know what configuration item I could have deliberately or accidentally set to cause that. Is there any setting or module that could cause that?

I don't think I have configured any Rules or Workflow settings to send emails, and it only occurs when the item is unpublished
The culprit turned to be the Antispam module, which is the client for the Akismet anti-spam system.

Its default setting causes an email to be sent to some administrators whenever a module is updated.

What baffled me was why that setting applied only when an unpublished item was created or updated.