We've configured foreman to send emails on failed puppet runs. The configuration is this:

1. Outgoing email settings

production:
delivery_method: :smtp
smtp_settings:
address: smtp.domain.net
port: 25
domain: domain.net
authentication: :none
tls: false
enable_starttls_auto: false

In foreman logs we noticed this error:

Failed to send email notification puppet_error_state: undefined method `recipients_for' for nil:NilClass