Invalid recipients are a fact of life for any mailer. You can minimize them with confirmed/double opt-in, but you still have typos and people who change their email addresses. We get that - it's cool.

At the same time, invalid recipients are used industry-wide as a metric of how good a mailing list is, and high invalid recipient numbers are associated with unsolicited mail and namespace mapping. That's not cool.

We've always factored invalid recipients into a sender's reputation, but we want to give you a heads up that we're refining the process a bit. As such, we would like to remind mailers that high numbers of invalid recipients is a Bad Thing and will result in poor delivery and removal from the whitelist.

Now, I know you, and you are asking, "What's a high number?" That's easy. A high number is a number higher than that which we consider indicative of a good mailer. If your invalid recipient stats are consistent with mailers similar to you, this shouldn't matter much to you. If you generate more invalid recipients than mailers similar to you, you will see a negative impact on your delivery in the near future.

David
Systems Programmer, AOL Postmaster Team