Reverse DNS (PTR)
Look up which host name a domain's IP address points back to.
About Reverse DNS (PTR)
What it is
The PTR record (Pointer Record) is the reverse of the A record: given an IP address, which domain does it point back to? This is called reverse DNS.
Why it matters
Receiving mail servers often check that the sender's IP address has a PTR record, and that it matches the announced host name. If the PTR is missing, mail can be rejected or end up in the junk folder.
Tips
- Ask your server or hosting provider to configure the PTR record, you can rarely do it yourself.
- The host name in the PTR should match what you used in SMTP HELO/EHLO.
- Check reverse DNS regularly if you change IP address.
Common questions
Why can't I set the PTR myself?
PTR is managed by whoever owns the IP address block, that is your hosting provider, not your DNS provider.
Is PTR enough for good mail delivery?
PTR is one of several requirements. SPF, DKIM and DMARC are at least as important, but PTR is often the first thing receiving servers check.
More lookups
MX lookup
See which servers receive mail for a domain, and which provider handles it.
SPF check
Check whether a domain has an SPF record and how strictly it rejects spoofed mail.
DMARC check
See whether a domain has DMARC and which policy it uses against spoofed mail.
DKIM check
Look for DKIM signing on a domain using the most common selectors.
DNSSEC check
See whether a domain is protected with DNSSEC, that is, whether its DNS answers are signed.
TXT lookup
List all TXT records for a domain, including SPF, verifications and more.
NS lookup
See which name servers control a domain's DNS.
Blacklist check
Check whether a domain's IP address is on blacklists such as Spamhaus, Barracuda and SpamCop.
A/AAAA lookup
See which IP addresses a domain points to, both IPv4 (A) and IPv6 (AAAA).
CNAME lookup
See whether a domain is an alias that points on to another domain.
SOA lookup
See the zone's core data: primary name server, contact and serial number.
CAA lookup
See which certificate authorities are allowed to issue certificates for the domain.
MTA-STS
See whether a domain requires encrypted mail delivery via MTA-STS.
TLS-RPT
See whether a domain receives reports about failed encrypted mail delivery.
BIMI
See whether a domain publishes a logo that can be shown in the recipient's inbox.
SSL certificate
Check a domain's TLS certificate: issuer, validity and expiry.
Whois
See who owns a domain, when it was registered and when it expires.
HTTP security headers
Check whether a domain's website sets important security headers.