Bottom line: The wrong domain is being returned to rDNS queries. I know PTR records aren't required and are somewhat controversial. The decision to have one or not is subjective. But when we do want one, I think it's important to be able to get the one we want. And I know this is a very common topic. But looking at my configuration, I still can't figure out what the problem is. I now have several domains in my ISPConfig environment. At this point, ISPConfig doesn't seem relevant to this question, I'm just saying this is what I'm using for management. The primary domain for this environment is primary.tld. Each of the domain zones has two NS records for "domain.tld.", with values ns1.primary.tld and ns2.primary.tld, respectively. In the primary domain zone these are the relevant records: Code: A primary.tld. 126.96.36.199 A mail 188.8.131.52 MX primary.tld. mail.primary.tld. 10 NS primary.tld. ns1.primary.tld. < this is .4 NS primary.t ns2.primary.tld. < this is .5 PTR 184.108.40.206.in-addr.arpa. mail.primary.tld. PTR 220.127.116.11.in-addr.arpa. mail.primary.tld. The secondary server is configured for mail but I have not created a secondary MX record for it yet. With "dig -x 18.104.22.168" on the localhost, the Answer section shows the actual server hostname: "myserver.primary.tld." and "myserver.". With "dig -x 22.214.171.124" (ns2) my ISPs node name for this IP is displayed, so that second PTR record is ignored/invalid. But the PTR record for 126.96.36.199 refers to the "mail" name anyway. So I'm confused about that. I'm thinking the only service that seems to care about RDNS is email. Postfix is set to display mail.primary.tld in the banner, so RDNS should return the same FQDN to make other email servers happy. Unfortunately on a rDNS query, one of the other zones is being returned, so the response is "other.tld", not "primary.tld" and not "mail.primary.tld". I'll certainly post more info as required. At this point I don't know what other info would help. Thanks!