Configure API Alerts for Weakened DMARC Policies
Email spoofing campaigns can look legitimate because a familiar domain appears in the From field. Monitoring should therefore inspect DNS policy and sender reputation, giving security staff a chance to act before fraudulent messages reach customers.
This guide shows how to configure the API to alert you when a critical domain's DMARC policy is weakened. Start by defining what critical means, capturing a trusted baseline and connecting each material change to a verified alert. The goal is early warning with enough context for a human to confirm intent and contain risk.
Trusted Sender Score is a free platform for domain reputation checks, DMARC and DKIM inspection, bulk checks and API access for embedding trust verification in existing workflows. Operated by Zulu Labs Inc., it suits individuals, domain owners and Australian security teams that need repeatable monitoring rather than ad hoc lookups.
Australian banks, fintechs, government portals and state services operate across .com.au, .gov.au and jurisdiction domains, while on-call staff may be spread across Sydney, Melbourne, Brisbane and Perth. Alerts need UTC timestamps, local business-hour routing and clear escalation ownership.
Set the critical-domain scope
Use bulk checking to assemble the candidate list, then retain domains that carry financial transactions, identity, payroll, customer support or regulatory messages. Include corporate aliases and delegated mail subdomains only where they can send externally, and assign an accountable owner to each.
For banks and payment providers, validate expected senders with the financial institution verification checklist before adding a domain to the critical tier. Separate customer-facing systems from internal or decommissioned names to suppress irrelevant alerts.
Capture a trusted baseline
Use the API to retrieve current domain trust and DMARC results, then inspect SPF and DKIM alignment settings and selectors in the underlying records. Save the raw response, record identifier, observation time and resolver result; a normalised summary can hide the relevant tag change.
Confirm the baseline with the domain owner or hosting administrator, especially if the API reports missing or inconsistent records. Follow the platform's documented authentication, endpoint and rate-limit rules for every request. Version each accepted baseline for reliable comparison.
Schedule reliable checks
Poll domains according to risk and DNS change processes. Critical payment or identity domains may warrant fifteen-minute or hourly checks, while lower-risk names can run daily. Respect resolver caches and prevent overlapping scheduled runs.
Store every result before the next comparison and make the checker idempotent. Distinguish an API failure from changed DNS; warning on every timeout trains responders to ignore alerts. A delayed alert is better than a false compromise claim.
Detect policy weakening
Compare each result with the last verified baseline, not merely the previous poll. Record improvements without weakening alerts, and use the DMARC policy guide to distinguish enforcement changes from reporting or subdomain settings. Raise a critical alert when enforcement is removed, relaxed, covers fewer messages or extends less reliably to subdomains.
| Baseline-to-current change | Security meaning | Automated response |
|---|---|---|
p=none becomes p=quarantine or p=reject |
Enforcement strengthens | Record improvement; no weakening alert |
p=reject or p=quarantine falls, or the record disappears |
DMARC enforcement weakens | Critical alert and verify with the owner |
pct is reduced |
Fewer failing messages receive enforcement | High warning; check rollout intent |
sp is reduced or removed |
Subdomain protection may weaken | High alert when the parent policy is permissive |
rua or ruf is removed |
Reporting visibility falls | Warning and contact the domain owner |
adkim=s or aspf=s becomes r |
More messages can qualify | High alert after owner confirmation |
Keep reporting and alignment signals separate. A domain can retain p=reject while removing rua visibility or relaxing strict DKIM and SPF alignment. Include changed fields and both records in the alert so responders need not repeat the investigation.
Deliver verified alerts
Map API changes into a payload containing domain, old and current policies, changed fields, severity, detection time and request identifier. Send critical changes through email, SMS or paging; route lower-severity events to chat or ticketing.
Secure any webhook endpoint you expose with HTTPS, secrets or signed requests, timestamp checks and replay protection. Follow the service's documented verification mechanism rather than guessing headers. Use idempotency, bounded retries and a dead-letter path to prevent lost or duplicate pages.
Tune severity and response
Use separate rules for financial, government and identity domains, ordinary corporate domains, and test environments. A rollback on a bank domain should page immediately; one on an unused marketing domain may only need a ticket. Owner confirmation should change urgency, not erase evidence.
Document the first response: freeze related configuration changes, inspect DNS history, SPF, DKIM and MX records, and search mail logs for unexpected senders. Assess personal information under the Privacy Act 1988 and Australian Privacy Principles, while keeping security notices distinct from commercial email covered by the Spam Act 2003.
Maintain the alert programme
Review thresholds quarterly and after incidents, migrations or ownership changes. Track time to detect, confirm, notify and remediate, plus false positives, duplicate events and overdue owner checks. Remove retired domains but retain final records for audit and threat intelligence.
Test the path with a controlled change in a safe domain, including API failure, webhook downtime and recovery. Many Australian teams use Microsoft 365 or Google Workspace with PagerDuty, ServiceNow or Splunk, so confirm links open safely and restrict sensitive DNS data in chat. Rotate credentials and grant least privilege.