[Koha] Overdue notices

I have a few questions about how others are handling overdue notices w/ Koha 3. If you're using Koha to send overdue notices via email, how do you keep track of overdues where the patron has not provided an email address? If an email address is no longer valid, do returned messages get bounced to the administrator? Any other tips on handling overdues? Many thanks, Cab Vinton, Director Sanbornton Public Library Sanbornton, NH