How do I add "bounceback" emails to the missing classmates page?

If the bounceback came from a classmate who has not joined the site, you can go to the bottom of the bounceback notification and click the Edit Classmate's Record button and remove the email address from their record. By definition, your Missing Classmates list is populated by classmates who do not have an email address on file. So, by removing the email address from his record, he should show up on the Missing Classmates page.