Exchange Help

Hello fellow colleagues. I need your expertise. Actually, I’m posting this on behalf of another colleague. Here’s the scenario. My friend works at a company who sends out a weekly publication. They email this publication via MS Exchange to their bulk email list of over 6000 subscribers. Here’s the problem. They get bounced back emails from addresses that are no longer valid and those bounce backs clog up the server. I am not an Exchange admin so I need your expert advice on this one. What do you recommend as a remedy? Is there also a tool that will capture the bad email addresses and export them say to an Exel spreadsheet? Thank you in advance for your help.