Most of that question involves a level of detail I can't get into. But, we use the same batch of IP addresses for all our mailings. We have authentication set

Most of that question involves a level of detail I can't get into. But, we use the same batch of IP addresses for all our mailings. We have authentication set up with SPF, DKIM, and DMARC, and we're very careful on our rate of delivery, and as above, we respond quickly to unsubscribes. As well as the occasional report of our mailings getting labeled as spam. We also partner with a reputation monitor that makes sure we're behaving, and they also let us know if we're approaching thresholds of not email friendly behavior. The only time I've seen that happen was when we did some IP consolidation and certain mail handling companies automated systems found our behavior anomalous, and thus was flagged suspicious. Since we knew, and our monitor knew this would happen, it was handled, and everyone (us, monitor, mail domains, customers) was running back to normal behavior within about two weeks. In the end, no blacklisting from this, and none while I've been here. We've had a fairly high inbox delivery rate (based on our rep monitor, about 3% higher than the average) over the years, and about the only thorn in my side is Comcast, and even our reputation monitor has "special" metrics to measure their customers in regards to Comcast. :)