Sometimes, a marketing or sales user may receive a "Delivery Status Notification" message indicating that an email failed to reach its intended recipient. In email parlance this is known as a bounce, and 99% of the time,these emails come back to Pardot and we will automatically handle this for you. The other 1% of the time, these emails wind up in your inbox.
Why does this happen?
Unfortunately, not all email servers follow the rules when it comes to responding correctly -- usually because they are running old, out of date software or are configured incorrectly.
What should you do with these emails?
We recommend you compile the email addresses from the emails that were undeliverable and manually opt out those prospects via an import.