An MX (Mail Exchange) record is a type of DNS record that specifies which mail servers are responsible for receiving email for a domain. MX records are essential for email delivery.
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An MX record is a DNS record that tells the internet which mail servers accept email for a domain. When someone sends an email to user@example.com, the sending mail server looks up the MX records for example.com to find out where to deliver the message.
MX records are one of several DNS record types — alongside A records (IPv4), AAAA records (IPv6), TXT records, and others. They are managed on the authoritative DNS side, not the resolver side.
Email delivery using MX records follows this process:
Each MX record includes a priority value (also called preference). Lower numbers mean higher priority. A domain can have multiple MX records for redundancy:
mail1.example.com — primary mail server, tried firstmail2.example.com — backup server, used if the primary is unavailablemail3.example.com — tertiary failoverThis priority system ensures email delivery continues even if a mail server goes down — the sending server automatically tries the next server in the list.
MX records are an authoritative DNS concept — they're configured by domain owners at their nameserver provider. Services like NOC.org manage authoritative DNS zones where MX records are created and maintained.
CleanBrowsing operates on the recursive resolver side — resolving DNS queries for end users. While CleanBrowsing's DNS filtering focuses on blocking web content domains, MX record lookups pass through normally since they're essential for email delivery.
Related DNS records for email security include TXT records used for SPF, DKIM, and DMARC — authentication mechanisms that verify email sender identity. For a deeper look at how DNS filtering complements email security tools, see our guide on DNS filtering and email security.