About the DNS Lookup
The DNS Lookup queries a domain for all common record types in one pass: A, AAAA, CNAME, MX, NS, TXT, SOA and CAA — each with its TTL. Ideal for verifying a DNS change has propagated, auditing SPF/DKIM/DMARC TXT records or checking which name servers are authoritative.
After changing records, remember that old values can stay cached for up to the previous TTL. Cross-check registration data with the Whois Lookup and mail/web reachability with the HTTP Status Checker.
A maps a hostname to an IPv4 address, AAAA to IPv6. CNAME aliases one hostname to another. MX records name the mail servers responsible for a domain, ordered by priority — lower numbers are tried first.
Time To Live is how many seconds resolvers may cache a record. Low TTLs (300s) let you switch servers quickly; high TTLs (86400s) reduce lookup traffic. Before a migration, lower the TTL a day in advance.
Mostly verification and email security: SPF (who may send mail for the domain), DKIM keys, DMARC policy, plus ownership proofs for Google, Microsoft and other services.