Notifier can automatically produce a recipient for user entities by calling AccountInterface::getEmail() method on a user entity instance.

Service parameter

User email behavior is enabled by default. You can configure whether this is on by modifying the notifier.field_mapping.user_email service parameter.

The parameter takes only true or false as its value.

For more information on service parameters, see Notifier configuration

Example

A user entity object which returns an email, will produce a recipient.

# Pseudo-code.
class \Drupal\user\Entity\User {
  public function getEmail() {
    // This method returns the value of the user entity's email field.
    return 'test@example.com'
  }
}

To add additional logic around the email address, consider configuring a bundle class to extend the User entity class, then override the getEmail() method.