How does a full circle reverse DNS check work?

Email marketer from Reddit explains that reverse DNS helps ensure that an IP address is legitimate and not associated with spam activity, increasing confidence among mail servers. This reputation boost can improve deliverability rates and reduce the chances of emails ending up in the spam folder.

Email marketer from EasyDMARC explains that to set up reverse DNS, you'll need to contact your ISP or hosting provider, as they control the PTR records for your IP address. You'll need to provide them with the hostname you want associated with your IP.

Email marketer from Stack Overflow responds that the purpose of reverse DNS is to resolve IP addresses to domain names, which is the opposite of what DNS normally does. This is used in many applications to verify the identity of a server or client.

Email marketer from DNSimple shares that reverse DNS helps establish trust and authenticity for email servers by matching IP addresses to domain names. This process is essential for email authentication protocols like SPF and DKIM, which help prevent spoofing and phishing attempts.

Email marketer from MXToolbox shares that a reverse DNS lookup is a DNS query that asks for the domain name associated with an IP address. This is the opposite of a forward DNS lookup, which asks for the IP address associated with a domain name.

Email marketer from Reddit explains that a full circle reverse DNS check (FCrDNS) involves checking both the forward and reverse DNS records. First, it checks if the IP address has a PTR record pointing to a hostname. Then, it checks if the A record of that hostname resolves back to the original IP address. This confirms the hostname is valid and authorized for the IP.

Email marketer from DigitalOcean explains that reverse DNS records, or PTR records, map IP addresses to domain names. This helps in verifying the authenticity of mail servers by ensuring the IP address is associated with a legitimate domain, which is a key factor in achieving email deliverability.

Email marketer from ReturnPath shares that having a properly configured FCrDNS record can significantly improve email deliverability. It helps establish trust with email providers and reduces the likelihood of your emails being flagged as spam, therefore your emails arrive in the recipient's inbox.

Email marketer from SparkPost shares that a reverse DNS record is important because it helps email providers verify that the server sending email from a specific IP address is authorized to do so. This can improve email deliverability by reducing the likelihood of emails being marked as spam.

Expert from Email Geeks explains that it's slightly more complex than that in practice, as there's not really any such thing as a reverse hostname. An IP address can have multiple PTR records, and a hostname can have multiple A and AAAA records. To check it you need to get all the PTR records and get all the A or AAAA records for each, and see if one of them matches. Some software gets that wrong, so if you have multiple PTR records some checkers might randomly decide it's good or it's bad each time they check.

Expert from Email Geeks shares that most of the time when they’re comparing the values they do the FCrDNS lookup IP -> hostname then hostname -> IP. Folks who suggest doing that may not even actually do the check comparing hostname and EHLO / HELO value unless there is something hinky about the EHLO/HELO value.

Expert from Spamresource explains that reverse DNS is a requirement for whitelisting at many ISPs. If you don’t have rDNS, or if it doesn’t match, you won’t get whitelisted, period.

Expert from Email Geeks explains that full circle DNS starts with the IP then looks up the PTR then looks up the A record associated with that PTR. Some will look up the HELO as well, but that’s separate from the FCrDNS and a lot of places have some level of mismatch between HELO and PTR for operational reasons, so the fact that they don’t exactly match shouldn’t hurt anything and where I say “a lot of places” I mean both ESPs and ISPs.

Expert from Word to the Wise shares that “forward-confirmed reverse DNS” (FCrDNS) is the correct configuration where a domain name resolves to an IP address and the IP address resolves back to the same domain name. This is a basic test that mail servers often use to help verify the identity of a sending server and helps in email authentication.

Expert from Spamresource explains that Reverse DNS (rDNS) is the opposite of forward DNS. Rather than using a hostname to look up an IP address, rDNS uses an IP address to look up a hostname. The system that makes this work is called a PTR record, which you generally get from whoever is providing the internet connection for the server.

Documentation from Microsoft Learn explains that reverse lookup zones in DNS allow you to use the IP address of a host to discover its name. This is the reverse of a forward lookup, where you use the name to find the IP address.

Documentation from ietf.org explains that PTR records map an IP address to a hostname. The query name is constructed by reversing the octets of the IP address and appending the domain 'in-addr.arpa'.

Documentation from IBM explains that within the reverse DNS zone file, PTR records are used to map IP addresses to their corresponding hostnames, enabling the reverse lookup process. In order for the reverse lookup to work, the PTR records must be properly configured to ensure accurate translation of IP addresses into hostnames.

Documentation from Cloudflare explains that rDNS records help verify the sending server's identity. They contribute to email deliverability and trust by confirming the server sending the email is authorized to do so for the domain in question, and it maps the IP address to a domain name.

Documentation from DNS Records explains that to configure a full circle reverse DNS check (FCrDNS), you need to ensure that both your forward and reverse DNS records are properly configured. The PTR record for your IP address should point to your hostname, and the A record for your hostname should point back to the same IP address.