What is FCrDNS?

What is Forward Confirmed reverse DNS or FCrDNS and how can it help bypass spam filtering?

Ivan Kovachev avatar
Written by Ivan Kovachev
Updated over a week ago

FCrDNS stands for Forward Confirmed Reverse DNS and it is used to show relationship between an IP address and domain name. To explain this let's look at the following examples:

Forward DNS:

example.com (domain) → (IP)

Reverse DNS: (IP) → example.com (domain)

FCrDNS means that the above Forward and Reverse DNS must match. In the above case they do so FCrDNS is confirmed. Although a weak form of authentication it is a good practice to have FCrDNS as it is used among many mail providers as an anti-spam method which in turn can help with email deliverability and placement. 

See also: Reverse DNS

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