Perlbug cannot know if the mail delivery happened to the final recipient. Perlbug hands off the mail to the local mail transfer agent (MTA), which hopefully forwards that mail to the next link in the chain. If sendmail (or whatever) is not configured to send outbound mail, hopefully it will send mail to root after the mail has lingered in its undeliverable state for some time. I don't know how Ubuntu handles its maili setup.