PTR Record (Pointer Record / Reverse DNS)

What Is a PTR Record?

A PTR record (Pointer record) is a type of DNS record that maps an IP address to a domain name — the reverse of what an A record does. This is called reverse DNS (rDNS). A PTR record for IP 203.0.113.42 might resolve to mail.company.com. Receiving mail servers check PTR records to verify that the sending IP has a legitimate, matching hostname — a basic sanity check that filters out many spam-sending botnets that operate from IP addresses with no reverse DNS configured.

Why PTR Records Matter for Email Deliverability

When your mail server connects to a receiving server, the receiver performs a reverse DNS lookup on your sending IP. If no PTR record exists, or if the PTR record doesn't match the forward DNS of the hostname (the A record for mail.company.com should resolve back to 203.0.113.42), many receiving servers will penalize the message or refuse delivery. Gmail, Outlook, and most enterprise mail gateways either require or strongly prefer that sending IPs have valid, matching PTR records.

PTR Record Setup

PTR records are managed by the owner of the IP address — which for most organizations is their hosting provider or ISP, not themselves. To set up a PTR record, you typically need to contact your hosting provider or ISP and request that they configure reverse DNS for your IP to point to your mail server's hostname. This is different from the forward DNS records you manage in your own domain's DNS zone. Cloud providers (AWS, GCP, Azure) provide interfaces for setting PTR records on Elastic/Static IPs.

PTR Record Mismatch

A PTR mismatch occurs when the hostname returned by a PTR lookup (reverse DNS) doesn't match the hostname that the mail server presents in its SMTP greeting (HELO/EHLO). For example, the PTR record says "mail.company.com" but the SMTP EHLO greeting says "smtp-outgoing-1.mailplatform.com." Mismatches are a common cause of deliverability problems that are easy to overlook. Check for PTR mismatches when troubleshooting inexplicable inbox placement issues.

Checking PTR Records

You can check any IP's PTR record with the dig -x command (e.g., dig -x 203.0.113.42) or using online reverse DNS lookup tools. MXToolbox provides a reverse lookup tool that checks both PTR records and MX records. EmailVerify.io's verification pipeline checks domain-level DNS configuration; for checking your own sending IP's PTR record, use the free DNS tools at emailverify.io/tools.

PTR Records and Blacklisting

Many blacklist organizations use the absence of a valid PTR record as a criterion for listing an IP. IPs with no PTR record or with PTR records pointing to generic ISP hostnames (indicating a residential or dynamic IP, not a legitimate mail server) are far more likely to be flagged as spam sources. If your sending IP appears on a blacklist and you can't identify the root cause, checking your PTR record configuration is a logical first step.