What reverse DNS is
Forward DNS turns a name into an address. Reverse DNS does the opposite: it asks which name an address claims, through a PTR record held by whoever owns the IP block — your hosting company or ISP, never you.
Why it matters for email
Mail servers check the sending IP's PTR before accepting a message. They want three things to line up: the IP has a PTR, the name in that PTR resolves back to the same IP (that is "forward-confirmed"), and the name looks like a mail server rather than a dynamic home connection. Fail any of them and your mail is treated as suspicious.
How to use the lookup
- Paste the IP addresses, one per line — up to ten at a time.
- Press Look up. Each PTR name is then resolved forward again to see whether it really points back.
- Read the last column. "Forward-confirmed" is what a receiving mail server wants to see.
Fixing a missing or wrong PTR
- You cannot set a PTR in your own DNS. Ask your hosting provider or ISP — most panels have a field for it.
- Set it to a name you control that also has an A record pointing back, such as
mail.yourdomain.com. - Changes can take a few hours to appear, and some providers do not offer PTR on shared hosting at all.
What it cannot tell you
- It does not list every site on a shared IP. One address has one PTR, no matter how many sites it hosts.
- A PTR proves nothing about ownership — it only shows what the IP block's owner chose to publish.
- Many home and mobile IPs have generic PTRs from the ISP, which is normal and not a problem unless you are sending mail from them.
Frequently asked questions
What is a PTR record?
A DNS record that maps an IP address back to a host name. It lives in the in-addr.arpa (IPv4) or ip6.arpa (IPv6) zone, controlled by whoever owns the IP range.
Why does my mail go to spam with no reverse DNS?
Receiving servers treat a missing or mismatched PTR as a sign of a compromised or careless sender. Ask your host to set a PTR that matches a name resolving back to the same IP.
Can I see every website on an IP address?
Not through reverse DNS. An address has one PTR record, while a shared server may host hundreds of sites. That needs a passive-DNS database, not a DNS lookup.