An SOA (Start of Authority) record specifies the DNS server providing authoritative information about an Internet domain, the email of the domain administrator, the domain serial number, and several timers relating to refreshing the zone.
SOA MNAME
This should state your primary nameserver.
ns1.example.com
SOA RNAME
This is the DNS contact e-mail address. Please note that the “@” should be replaced by a period (.).
hostmaster.example.com
SOA Serial #
This should be set automatically, and preferably be time and date based. The recommended format is YYYYMMDDnn, where ‘nn’ is the revision.
SOA REFRESH value
RFC1912 suggests 20 minutes to 2 hours, if bandwidth isn’t an issue (1200 to 7200 seconds).
SOA RETRY value
The retry value is the amount of time your secondary/slave nameservers will wait to contact the master nameserver again if the last attempt failed. This value is typically some fraction of the refresh interval, e.g. 15 minutes (900 seconds).
SOA EXPIRE value
RFC1912 suggests 2-4 weeks (1209600 to 2419200 seconds).
SOA MINIMUM TTL value
RFC2308 suggests a value of 1-3 hours (3600 to 10800 seconds).
