Ask HN: Where to buy Reverse DNS lookup database from?
You can look it up yourself, but watch out for CDN's and other third-party services and be aware that not every IP address has a reverse DNS entry. On MacOS:
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Note that the IP address bytes are reversed in the following command to lookup 18.9.25.15
host -a 15.25.9.18.in-addr.arpa
;; ANSWER SECTION:
15.25.9.18.in-addr.arpa. 1800 IN PTR dmz-mailsec-scanner-4.mit.edu.
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host -a dmz-mailsec-scanner-4.mit.edu
;; ANSWER SECTION:
dmz-mailsec-scanner-4.mit.edu. 1800 IN A 18.9.25.15
dmz-mailsec-scanner-4.mit.edu. 1800 IN HINFO "VMWARE/VM" "LINUX"