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SOA is an acronym for Start of Authority which is a set of DNS information assigned to every domain name upon registration, precisely at the moment of delegation from its parent domain.

Most domain or DNS service providers do not permit basic customers to modify SOA records themselves but this can be done by authorized agents or support teams upon customers’ request.

Not to worry, every SOA record gets updated automatically when DNS settings are changed. For instance, if you changed your domain nameservers or modified other DNS records such as the A, CNAME, or MX records, your SOA record will get updated as well, especially the serial number.

The SOA record for each domain contains 7 required details which include, the primary nameserver, domain admin email, serial number, refresh interval, fail-retry interval, expiration time, and the default TTL (Time-to-Live).

Here is a sample of an SOA record for testingforzcomph.com.

Primary Nameserver

This is the host name for the primary DNS server for a domain zone. In most cases, you will find that domain names are assigned 2 or 3 nameservers, the SOA record will simply pick the first nameserver as primary. From the example above, ns-a1.cloud.z.com is the primary nameserver for testingforzcomph.com.

Admin Email

This is the email address of the party or individual that is responsible for administering the domain’s zone file, it is mostly the email address of the registrant. As shown in the above example, the email address is most times presented like a subdomain, hence, the email address is postmaster@testingforzcomph.com in place of postmaster.testingforzcomph.com.

Serial Number

The serial number is a timestamp that is automatically assigned and changes whenever a DNS setting is updated. From the result above, the serial number for the zone is 1580420183.

Refresh Interval

This is the time in seconds that the DNS server waits before refreshing the SOA record to check for changes. 3600 seconds is the refresh interval that is set for testingforzcomph.com zone.

Fail-Retry Interval

This is usually shorter than the Refresh interval because, it is the number of seconds that the DNS server has to wait before a failed refresh should be retried. The example above shows 600 seconds for testingforzcomph.com zone.

Expiration Time

A secondary DNS server always gets its information updated via a primary DNS server, hence, when it checks for updates or tries to synchronize data and cannot connect over a period of time, it will consider the primary DNS zone as no longer authoritative or valid. This is known as the expiration time on an SOA record and the example above has 86400 seconds set for testingforzcomph.com zone.

Default TTL

The time-to-live is a value that applies to all resource records in the zone, which is supplied to inform other servers of how long they should keep the zone data in their cache.  As shown above, the default value is 3600 seconds. After this period, a resolver assigns a negative result for a subdomain and then retry.

In conclusion, it is good to know about your domain SOA record and how it interacts with the connected DNS servers, especially when using a third party provider. You can view the SOA record for your domain on ViewDNS.info and if you intend to change any of its details, feel free to contact Z.COM support team for assistance.