A records vs PTR records
A records and PTR records are two sides of the same coin: one maps a name to an IP, the other maps an IP back to a name. They’re easy to confuse, but knowing the difference is essential for anyone running a server or troubleshooting email.
The A record: name → IP
An A record (Address record) maps a domain or subdomain to an IPv4 address. When someone visits example.com, DNS uses the A record to find the server’s IP. This is forward DNS — the everyday lookup that makes the web work. The IPv6 equivalent is the AAAA record. You control your A records in your domain’s DNS settings.
The PTR record: IP → name
A PTR record (pointer record) does the reverse: it maps an IP address back to a hostname. This is reverse DNS. Unlike A records, you don’t control PTR records in your own DNS — they’re managed by whoever owns the IP block (your ISP or hosting provider), because they live in a special reverse zone tied to the IP, not your domain.
Side by side
Think of it as a phone book working two ways. The A record is looking up a person’s name to find their number. The PTR record is caller ID — seeing a number and finding whose it is. A healthy mail server needs both to agree: the A record points the name at the IP, and the PTR points the IP back at the name (see FCrDNS).
Why does the A vs PTR distinction matter?
Most people only ever set A records, which is why PTR records cause confusion when email starts failing. If your mail server’s reverse DNS is wrong, you can’t fix it by editing your domain’s DNS — you have to ask your IP’s owner. Understanding which record lives where saves hours of troubleshooting.
Checking both directions
Use our Reverse DNS tool to see the PTR (the IP’s hostname). A normal DNS lookup of a domain shows its A record. When you’re setting up a mail server, confirm both point at each other.
Related: What is a PTR record? · IP address FAQ