@jwildeboer I don't see how it will make the blacklists any larger. Big Mail (to the extent they are affected) will fix it on their inbound, and the blacklists aren't likely to add servers to the lists that still can be verified via IP-based means like SPF. It's not like this can't be figured out. I haven't seen any sendmail mitigation, by the way, except something that might apply to the very latest version that doesn't even run widely.