Reverse DNS Checker
Verify that your sending IP address has proper reverse DNS (PTR) records configured and that they match forward DNS.
What is Reverse DNS?
Reverse DNS (rDNS) is the process of resolving an IP address back to a hostname using PTR (Pointer) records. It is the opposite of a regular DNS lookup, which resolves a hostname to an IP address. In the context of email, reverse DNS is used by receiving mail servers to verify that a sending IP address has a valid hostname associated with it.
Why Reverse DNS Matters for Email
Many mail servers check reverse DNS as part of their spam filtering. If a sending IP does not have a PTR record, or if the PTR record does not match the forward DNS (A record), the email may be rejected or flagged as suspicious. Proper rDNS setup signals that the IP is associated with a legitimate mail server.
Forward-Confirmed Reverse DNS (FCrDNS)
The gold standard for rDNS is forward-confirmed reverse DNS. This means:
- The IP address has a PTR record that resolves to a hostname.
- That hostname has an A record that resolves back to the same IP address.
Our tool checks both directions automatically, confirming whether your rDNS setup meets this standard.
How to Set Up Reverse DNS
Unlike regular DNS records, PTR records are managed by the owner of the IP address, not the domain owner. To set up rDNS:
- Contact your hosting provider or ISP.
- Request that they create a PTR record for your IP address pointing to your mail server's hostname.
- Ensure the hostname also has a matching A record pointing back to the IP.
If you use a cloud provider (AWS, Google Cloud, Azure, etc.), they typically have a self-service option for configuring rDNS on your allocated IP addresses.
Frequently Asked Questions
Reverse DNS (rDNS) resolves an IP address back to its associated domain name, the opposite of standard forward DNS. It works by querying a PTR (Pointer) record. For IPv4, the IP is reversed and appended with .in-addr.arpa. Email servers and security tools commonly use reverse DNS to verify the identity of connecting servers.
Reverse DNS is critical because most major email providers (Gmail, Yahoo, Microsoft) check for valid rDNS on the sending server and may reject or spam-filter emails from IPs without proper reverse DNS. A valid PTR record adds credibility by proving the IP address owner has explicitly associated it with a domain name.
A PTR record maps an IP address to a domain name, while an A record maps a domain to an IP -- they are the reverse of each other. PTR records are stored in a reverse DNS zone managed by the IP block owner (typically your hosting provider), not in your domain's regular DNS zone.
Contact your hosting provider or ISP, as they manage the reverse DNS zone for your IP address block. Request a PTR record mapping your mail server's IP to its hostname (e.g., mail.yourdomain.com). Ensure the hostname has a matching A record pointing back to the same IP, creating Forward-Confirmed Reverse DNS (FCrDNS).
FCrDNS is a verification method where the reverse DNS lookup of an IP returns a hostname, and the forward lookup of that hostname returns the same original IP. This two-way match provides stronger verification than a simple rDNS lookup alone. Most email servers and spam filters check for FCrDNS.
Use our reverse DNS checker by entering your mail server's IP address to see if a PTR record exists and what hostname it resolves to. The tool also verifies that the returned hostname resolves back to the same IP (FCrDNS check). You can also use the command line: dig -x YOUR_IP_ADDRESS on Linux/Mac.
If no PTR record exists for your IP, many email servers will reject your emails outright or assign a significantly higher spam score. Your sending IP may also be more likely to end up on blocklists. Google and Yahoo's sender requirements explicitly mandate valid reverse DNS, meaning failed rDNS can block your emails from reaching major platforms.
PTR records are managed by the entity that owns or controls the IP address block, typically your ISP, hosting provider, or cloud provider (AWS, Google Cloud, Azure). Unlike standard DNS records that you manage through your domain registrar, you cannot create PTR records in your own DNS zone. Most providers offer a control panel option or support ticket process for rDNS setup.