How do I check if the sending IP address matches the IP address of the hostname specified in the Pointer (PTR) record?
Summary
What email marketers say12Marketer opinions
Email marketer from Reddit explains to use `nslookup <ip_address>` in your terminal to perform a reverse DNS lookup. The output will show the hostname associated with the IP. Compare this hostname with the expected hostname.
Email marketer from DMARCly shares that to check if the sending IP matches the hostname in the PTR record, you need to perform a reverse DNS lookup. You can use online tools or command-line tools like `dig` or `nslookup` to query the IP address and retrieve the hostname. Then, verify that the hostname resolves back to the original IP address.
Email marketer from Email Geeks recommends focusing on clients that have a Dedicated IP (DIP) as those are the ones that may break things because brands can have people who manually manage the DNS, and new folks don't understand why this record is here and delete it.
Email marketer from WhatIsMyIP explains to utilize the Reverse DNS Lookup tool on WhatIsMyIP.com to enter the IP and verify if the hostname matches the IP address.
Email marketer from EasyDMARC explains that to check the PTR record, use online tools like their own PTR Record Lookup tool. Enter the IP address to see the corresponding hostname. This helps verify if the PTR record is correctly configured and matches the sending IP.
Email marketer from DNSQueries shares that they offer a Reverse DNS Lookup tool. Enter the IP address and check if the hostname matches the expected hostname, ensuring proper PTR record configuration.
Email marketer from Email Geeks shares that a FCrDNS needs to be complete. Where the PTR points to the domain/hostname and the hostname points to the IP.
Email marketer from MXToolbox shares that MXToolbox offers a Reverse DNS Lookup tool where you can enter an IP address to check the associated PTR record. It will show if the record exists and the hostname it resolves to, helping you ensure the sending IP matches the hostname.
Email marketer from Email Geeks shares that, for those that like doing things from bash, nmap has a very handy fcrdns script to check forward-confirmed reverse DNS on an IP and provides an example.
Email marketer from Wormly explains that Wormly offers a tool to check reverse DNS records. You provide the IP address, and it shows the associated hostname, allowing you to verify if it matches the expected hostname.
Email marketer from Namecheap shares that you can use online reverse DNS lookup tools to check PTR records, and they also provide some tips on PTR record setups.
Email marketer from StackOverflow explains to use online reverse DNS lookup tools. Input the IP address, and the tool will display the associated hostname. Ensure the hostname matches the IP address.
What the experts say4Expert opinions
Expert from Email Geeks shares that every smarthost you have needs to have its own hostname, and you need to set up an A record from that hostname to the smarthosts IP address, and a PTR record from that IP address to the hostname.
Expert from Word to the Wise explains that the core of checking is verifying that forward and reverse DNS match. This is known as Forward Confirmed reverse DNS, or FCrDNS. You can use online tools to help confirm this is setup correctly.
Expert from Email Geeks explains the only place you’ll _typically_ see the actual hostname of the server is in the HELO (often recorded in a Received header) and where an intermediate server does that reverse DNS lookup for you and records that in a Received header. Neither of those are 100% guaranteed to be there.
Expert from Email Geeks explains to start with the hostname, look it up to get an IP address, then look up the IP address to get a hostname. If it matches where you started, you’re good.
What the documentation says5Technical articles
Documentation from RFC Editor specifies that a properly configured PTR record should match the corresponding A record. To verify, first resolve the IP address to a hostname using reverse DNS. Then, resolve the hostname back to an IP address using forward DNS. The IPs should match.
Documentation from Cloudflare Support explains that when you create or modify a PTR record, you can use online tools to check propagation. Ensure the IP address resolves to the correct hostname.
Documentation from Microsoft explains that for Windows servers, you can use the `nslookup` command to query the PTR record. Open Command Prompt and type `nslookup <IP_address>`. The result will show the hostname if the PTR record is correctly configured.
Documentation from DigitalOcean Community explains that after setting up a PTR record, you can verify it by using the `dig` command. For example, `dig -x your_ip_address` will return the hostname associated with the IP. Confirm that the hostname is what you expect it to be.
Documentation from Google Workspace Admin Help explains you can use online tools like IntoDNS or MXToolbox to check your PTR record. These tools allow you to enter your IP address and see if the PTR record is correctly set up and pointing to your domain.