DNS checks

The DNS check queries your domain's full record set every hour by default and compares the result to the previous snapshot. If any record changes, disappears, or indicates a mail deliverability problem, DomainCare fires an alert. You get signal on real changes, not noise from transient resolver hiccups.

What it monitors

• A / AAAA records — IPv4 and IPv6 addresses the domain resolves to, plus their TTL values
• CNAME records — canonical name targets
• MX records — mail exchanger hostnames and priorities
• TXT records — the full set of TXT strings (includes SPF, verification tokens, etc.)
• NS records — nameserver hostnames reported by the zone
• SOA record — primary nameserver (nsname) and serial number
• CAA records — certificate authority authorization entries (issue, issuewild, iodef)
• PTR / reverse DNS — reverse DNS names for the first five resolved IPs
• MX PTR (FCrDNS) — forward-confirmed reverse DNS check on the primary MX host

How often it runs

The DNS check runs every 1 hour (3,600 seconds) by default. Pro and Business plans can override this to a faster interval per domain via per-check controls. A single differing result triggers an alert immediately — there is no consecutive-failure debounce for record changes, since a changed record is a real state change. The MX PTR check is included in every run; it resolves the primary MX exchange, looks up its A record, and verifies the PTR name matches.

Alerts this check produces

Event	Tone	When it fires
dns_records_changed	Warning	One or more A, AAAA, or NS records changed from the previous snapshot
cname_records_changed	Warning	CNAME target changed
mx_records_missing	Failure	All MX records disappeared (no mail exchangers found)
mx_records_changed	Warning	MX records changed (different exchangers or priorities)
mx_recovered	Recovery	MX records are present again after a mx_records_missing event
txt_records_changed	Warning	TXT record set changed
resolved_ip_changed	Warning	The IP addresses the domain resolves to changed
caa_records_changed	Warning	CAA record set changed
caa_records_missing	Warning	No CAA records found (domain had CAA records previously)
caa_recovered	Recovery	CAA records are present again after a caa_records_missing event
soa_primary_ns_changed	Warning	The SOA nsname (primary nameserver) changed
mx_ptr_mismatch	Failure	Primary MX PTR name does not match the MX hostname (FCrDNS failed)
mx_ptr_missing	Warning	Primary MX host resolved to an IP but no PTR record exists
mx_ptr_recovered	Recovery	MX PTR is correct again after a mismatch or missing event
dns_ttl_dropped_low	Info	A record TTL dropped below the low-TTL threshold (signals upcoming change or misconfiguration)

What to do when alerts fire

• dns_records_changed / resolved_ip_changed — verify the change was intentional (deployment, CDN migration, DNS provider change). If you did not make the change, check your DNS provider for unauthorized edits and rotate any API keys that have write access.
• mx_records_missing / mx_records_changed — missing or changed MX records will interrupt email delivery immediately. Restore the correct MX records and confirm with a live mail test.
• caa_records_missing — without CAA records any CA can issue certificates for your domain. Add a CAA record that restricts issuance to your CA of choice (e.g. 0 issue "letsencrypt.org").
• mx_ptr_mismatch / mx_ptr_missing — many spam filters reject mail from servers without matching FCrDNS. Ask your mail host or hosting provider to set a PTR record for the mail server IP that matches the MX hostname.
• dns_ttl_dropped_low — a TTL under 300 seconds suggests a DNS change is in progress. Normal after intentional migrations; investigate if unexpected.

Related

• Email deliverability — SPF and DMARC depend on correct TXT and MX records
• Nameserver checks — monitors authority and NS record validity
• Alert reference