What is FCrDNS?

FCrDNS stands for Forward Confirmed Reverse DNS. It is an email verification method used to confirm that a given IP address is associated with a domain name, and vice versa. This is done by performing two DNS lookups:

Reverse DNS Lookup: It starts with an IP address and queries DNS for the domain name associated with that IP.

For example, if the IP is 192.0.1.1, the reverse DNS might return the hostname mail.example.com.
Forward DNS Lookup: It then takes the obtained hostname and queries DNS again to find the IP address associated with it.

In our example, querying mail.example.com should return 192.0.1.1.

If the IP address obtained from the forward DNS lookup matches the original IP address, the FCrDNS check is considered successful.

Who Sets It Up?

FCrDNS setup is typically done by the owner of the domain name and the owner of the IP address. These may or may not be under the control of the same party. If you don't own the IP address, you may need to contact your hosting service provider or ISP to set up the reverse DNS.

How It Helps with Deliverability

FCrDNS is particularly important in email deliverability for several reasons:

Spam Prevention: Many email servers perform FCrDNS checks to verify the sender's domain. A successful FCrDNS check indicates that the sender is more likely to be legitimate, reducing the chance of being marked as spam.
Reputation: Domains with properly configured FCrDNS are often considered more trustworthy, improving their reputation among email providers.
Security: FCrDNS can help identify and block fraudulent or spoofed email addresses, enhancing overall email security.
Both Google and Yahoo will start requiring it starting February 2024.

In summary, FCrDNS is a crucial element in network and email security, helping to authenticate connections and improve the reliability and trustworthiness of online communications.

Can I easily test my FCrDNS configuration?

Yes, you can use our Investigate tool to test your email set up here. Alternatively, if you are already an OnDMARC customer, you can find the Investigate tool within your OnDMARC account, under Tools.