Reverse DNS / PTR Lookup

What reverse DNS is for

"Forward" DNS converts a name to an IP (myipcat.com → 104.21.51.82). Reverse DNS does the opposite — given an IP, it returns the hostname (if one is set). Reverse DNS uses PTR records published in the in-addr.arpa (IPv4) or ip6.arpa (IPv6) zones.

Where PTR records actually matter

• Email deliverability — receiving mail servers reject (or score as spam) email from sending IPs without matching PTR/forward records. If you run your own mail server, set up PTR or your mail goes nowhere.
• Log analysis — server logs are full of IPs. PTR lookups make them human-readable: 52.85.132.45 becomes server-52-85-132-45.bos2.cloudfront.net.
• SSH brute-force detection — sketchy login attempts often come from IPs with weird or missing PTR records.
• IP reputation — many reputation services use PTR records as a signal.

Who controls the PTR record?

The PTR record is controlled by whoever owns the IP block — typically your ISP or hosting provider, not you. To get a custom PTR (e.g. mail.example.com), you submit a request to your provider. Some self-service providers (AWS, OVH, Hetzner, Vultr) let you set it via their dashboard.