DNS

What is DNS?

DNS (Domain Name System) is the internet's address book. It translates human-readable domain names (like mailchk.io) into the IP addresses that computers use to locate each other. Without DNS, you'd need to remember IP addresses like 104.18.32.7 instead of domain names.

For email, DNS is critical — it stores the records that tell the internet where to deliver email (MX records), who's allowed to send email (SPF), and how to authenticate messages (DKIM and DMARC).

DNS Record Types for Email

• MX records — Specify which mail servers receive email for the domain.
• TXT records — Store SPF policies, DKIM public keys, and DMARC policies as text strings.
• A/AAAA records — Map hostnames to IP addresses (used to resolve mail server hostnames from MX records).
• PTR records — Reverse DNS — map IP addresses back to hostnames. Used by receiving servers to verify sender legitimacy.
• CNAME records — Aliases that point one hostname to another. Sometimes used for DKIM selectors.

DNS and Email Validation

Email validation relies heavily on DNS. When validating an email address, the validator queries DNS to check whether the domain has MX records (can it receive email?), what SPF policy is set (who can send from it?), and whether the domain has proper DKIM and DMARC configuration. A domain with no DNS records at all is invalid — any email address at that domain will bounce.