If you send emails from your domain, whether marketing or just transactional, DMARC is important to maintaining domain reputation and making sure your emails don't go to spam.

DMARC Report makes it *really* simple to track multiple domains and keep an eye out for issues. Hopefully it never matters, but if you ever have a bad domain IP or hackers using your email addresses, you'll be glad you can identify the problem and figure out the best solution.