A Fully Qualified Domain Name (FQDN) is the complete, unique address of a specific host or service on the internet. It includes all domain levels, from the host name up to the top-level domain (TLD).
For example, mail.example.com is an FQDN, while example.com by itself is just a domain name. The FQDN identifies one exact location in the DNS hierarchy, making it essential for routing email and web traffic correctly.
An FQDN typically follows this structure:
[host].[subdomain].[domain].[top-level domain]
Each part of the name is separated by a dot. For example:
When you see a trailing dot at the end (like mail.example.com.), that represents the absolute root of the DNS tree, though it’s usually omitted in everyday use.
FQDNs are fundamental to how the internet and email systems operate because they allow computers and mail servers to find the exact destination for a given service.
In email, FQDNs are used in DNS records to define critical components such as:
Without properly configured FQDNs, email delivery and authentication can fail, leading to lost messages or security vulnerabilities.
DMARCeye helps organizations monitor the DNS records that depend on accurate FQDNs, including SPF, DKIM, and DMARC configurations.
By analyzing DMARC reports and DNS data, DMARCeye reveals which FQDNs are being used to send or authenticate email on behalf of your domain. This visibility helps identify misconfigurations, unauthorized hosts, or missing DNS entries that can affect both security and deliverability.
With DMARCeye, teams can ensure that every FQDN in their mail infrastructure is properly aligned and authenticated.
Sign up for a free trial of DMARCeye today to start protecting your email domain.
To learn more about DMARC and DMARC-related terms, explore the DMARCeye Glossary.