A record
The DNS record that maps a host name to an IPv4 address, such as mail.example.com to 192.0.2.25.
What it means
An A record holds one 32-bit IPv4 address; a name can have several. In mail, the host names in MX records must have A or AAAA records, a server's HELO name should resolve to its own address, and forward-confirmed reverse DNS requires the PTR name's A record to point back to the sending IP.
SPF's a mechanism also reads them: a or a:host matches the sending IP against the A records (or AAAA records for IPv6 connections) of the name given.
An MX target must hold A or AAAA records directly, never a CNAME, according to RFC 2181.
Example
mx1.example.com. 3600 IN A 192.0.2.25Related terms
On this site
Sources
What this definition rests on. The wording is ours; the facts are theirs.
All 432 terms in the glossaryThe wiki: blocklists and bounce codes