What is a DNS SOA record?

An SOA (Start of Authority) record defines the authoritative DNS zone for a domain. It specifies the primary nameserver, the zone administrator's contact, a serial number for zone synchronization, and timing values for how secondary nameservers refresh and expire zone data.

What does the SOA serial number mean?

The SOA serial number is incremented each time the zone is updated. Secondary nameservers compare the serial to decide whether to pull a fresh copy of the zone. It is often in YYYYMMDDNN format, where NN is the change count for that day.

SOA Record Lookup - Check Start of Authority for Any Domain

Q: Does the SOA record affect email delivery?

Indirectly. The SOA minimum TTL controls how long failed DNS lookups are cached. A high minimum TTL means DNS fixes (like updating SPF or DMARC) take longer to propagate to resolvers that cached a negative response.

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Look up the SOA (Start of Authority) record for any domain. See the primary nameserver, responsible contact, serial number, refresh, retry, and expiry settings.

SOA record fields explained

Field	What it means
mname	Primary nameserver - the authoritative nameserver that holds the master copy of the zone.
rname	Responsible mailbox - the email address of the zone administrator, encoded with a dot instead of @.
serial	Zone serial number - incremented each time the zone is updated. Secondary nameservers use this to detect changes. Often in YYYYMMDDNN format.
refresh	How often secondary nameservers check the primary for zone changes (in seconds). Typical value: 3600–86400 seconds.
retry	How long a secondary nameserver waits before retrying a failed zone transfer. Typical value: 600–7200 seconds.
expire	How long a secondary continues serving zone data if it cannot reach the primary. Typical value: 604800–2419200 seconds (1–4 weeks).
minimum TTL	The negative caching TTL - how long a NXDOMAIN (non-existent domain) response is cached. Affects how long DNS changes take to propagate for deleted records.

SOA serial number and DNS propagation

The SOA serial number is how secondary nameservers know when to refresh zone data. When you update a DNS record (like SPF or DMARC), your DNS provider increments the serial number. Secondary nameservers periodically check the serial, and if it increased, they pull a fresh copy of the zone. If propagation seems slow, checking whether the serial number is updating correctly can help diagnose the issue.

FAQ

What is an SOA record used for?

The SOA record defines the start of a DNS zone. It specifies which nameserver is the primary authority, who manages the zone, and how secondary nameservers should synchronize. Every DNS zone must have exactly one SOA record.

Does the SOA record affect email delivery?

Indirectly. The SOA record controls DNS zone synchronization. If the minimum TTL (negative caching TTL) is very high, failed DNS lookups take longer to resolve after you fix them. The serial number update cadence also affects how quickly secondary nameservers pick up changes to your MX, SPF, or DMARC records.

What does the SOA rname field mean?

The rname field stores the email address of the zone administrator, but with @ replaced by a dot. For example, admin.example.com. represents [email protected]. This is a technical contact for DNS-level issues and is rarely used in practice.