Overdue notices that have been emailed can be manually re-sent by setting up specific email routing rules and choosing the rule using the Send E-mail button on the Borrowing Overdues ribbon. The email template for the rule that you have chosen, merged with item-specific data, will appear. You can make changes to the text before sending if you wish. Once you've made the necessary changes, choose to Send to send the email. A copy of this email is saved in ILLiad and can be seen by accessing the Email History using the History tab of the Request Form. Note that manually resending emails does not modify the LastOverdueNoticeSent value.
See Adding Email Routing Rules for information on creating and using email routing rules.