`A` Address Record (IPv4)

An A record maps a hostname to an IPv4 address. Learn how A records relate to mail servers, SPF, and FCrDNS checks.

Record Type
A

Category
Address & Routing

RFC
RFC 1035

Email Relevant
Yes

Format
A <ipv4-address>

Example
A 93.184.216.34

TTL Guidance
3600 s typical; 300 s during migrations or failover testing

💬 What This Record Does

An A record is the simplest DNS record: it maps a hostname to an IPv4 address. When your browser or mail server needs to connect to example.com, it queries the A record to find the IP address. For email, A records are used by MX hosts (your mail server's hostname must have an A record), by the SPF "a" mechanism (which authorises the IP in an A record), and by FCrDNS checks (the PTR hostname must resolve forward via an A record back to the sending IP).

Common Uses

Resolving your mail server hostname to an IP for MX routing
Being referenced by the SPF "a" mechanism
The forward lookup half of an FCrDNS (PTR ↔ A) check

⚠️ Watch Out For

MX records must point to hostnames, not bare IPs. The hostname needs an A record.
If your A record changes and SPF uses the "a" mechanism, your SPF authorised set changes silently.