The one thing you do NOT want to do when you get a returned email is to change the email address to a fake one like  

Instead, check the Wrong email address flag on the member's account.  You can access this flag anywhere an email address can be entered, such as through the Name/Address button (F14) in Inquiry and Phone Operator, or via Tool #14 "Member Personal Banker" (shortcut: pb), or via Tool #15 "Update Membership Information" (shortcut: umbr).

When a member's email address is flagged as wrong, the system automatically omits them from subsequent emails, including e-Statement notifications, marketing emails, etc.

Use the related link below to learn more about how CU*BASE handles wrong email addresses when emails are sent via CU*BASE (such as those sent through Member Reach or as e-Alerts or e-Statement reminders).