Email Deliverability Checklist for Healthcare and Compliance

Document how messages move from MX intake through parsing, webhooks, storage, and EHR endpoints. This enables HIPAA risk analysis and highlights where deliverability failures could expose PHI or block care workflows.

Choose between on-premise, private cloud, or vendor-hosted processing and ensure a signed BAA where applicable. Scope which domains, mailboxes, and APIs will handle PHI to align controls and audit boundaries.

Require TLS 1.2+ with approved cipher suites for SMTP and HTTPS and enforce mTLS for webhook delivery where feasible. Publish and enforce a policy that quarantines non-compliant connections rather than silently dropping messages.

Maintain IP ranges and domains for trusted senders such as labs, pharmacies, and payers to reduce false positives in anti-abuse checks. Use the allowlist to bypass aggressive filtering without skipping AV/DLP scanning.

Define allowed types (PDF, CDA, HL7, DICOM) and maximum sizes per use case and reject or quarantine non-compliant items. Communicate limits to partners to reduce retries and ensure predictable parsing.

Set message and attachment retention periods, automatic redaction rules for notifications, and explicit deletion timelines. Align with minimum necessary principles and legal hold exceptions.

Create runbooks for NDR handling, quarantine release decisions, and partner notifications that avoid echoing PHI. Include isolation procedures and audit trails for investigative needs.

Use domain segregation such as phi.example.org for clinical traffic and route to hardened MX hosts. Dedicated MX paths simplify policy enforcement and auditing.

Reduce TTLs 48-72 hours before migration, validate receipt in staging, then raise TTLs post-cutover. This limits propagation issues and reduces message loss during transitions.

Ensure SMTP TLS certificates present names that match MX hostnames and verify PTR records map consistently to A records. Misaligned identity causes handshake failures and missed mail.

Publish TLSA records to pin server keys and strengthen inbound SMTP encryption for partners that validate DANE. This adds resilience against downgrade attacks.

Create distinct namespaces and MX routes for PHI and administrative mail and enforce independent policies. Segregation reduces blast radius and improves deliverability predictability.

Quarantine and review failures instead of outright rejecting to avoid losing forwarded or aliased messages common in clinical referrals. Preserve authentication results in headers for audit.

Add ARC headers to preserve sender authentication results through your system if you relay to internal or external mailboxes. This helps downstream DMARC evaluation and reduces false positives.

Accept only TLS 1.2+ with vetted cipher suites and quarantine cleartext or weak-negotiation sessions. Log handshake results for compliance evidence.

Correctly handle nested multipart structures, charsets, and encodings while preserving raw headers for chain-of-custody. Avoid lossy transformations that hinder clinical interpretation.

Recursively unpack archives, block macro-enabled office files, and detect zip bombs with depth and expansion limits. Route suspicious items to a sandbox queue for analyst review.

Integrate with HSM or KMS for key custody, decrypt content for processing, and record signature validity in the audit trail. Preserve encrypted originals for evidentiary needs.

Use streaming parsers for bodies and attachments and set per-message limits appropriate to DICOM and imaging workflows. Apply backpressure to protect downstream services.

Use policy-based detectors for identifiers such as MRN, claim numbers, or ICD codes and tag messages for restricted handling. Send alerts without echoing PHI content.

Reject or sanitize HTML with scripts and block executable formats while allowing clinical standards such as CDA or HL7. Document exceptions and approvals in the audit log.

Sign every delivery with an HMAC header, rotate secrets on a schedule, and require client-auth TLS where supported. Validate signatures before processing to prevent spoofing.

Include stable message IDs and content hashes so receivers can safely retry and de-duplicate deliveries. This eliminates double-ingestion during transient failures.

Retry failed webhooks with capped backoff and route exhausted attempts to a DLQ with alerts. Provide operators a replay workflow with reason codes.

Offer a read-only polling endpoint for maintenance windows or partner firewalls and publish SLAs for availability. Throttle and page results to protect downstream systems.

Attach SHA-256 hashes for bodies and attachments, original SMTP timestamps, and authentication results. Downstream systems can verify integrity and store evidence fields.

Use per-tenant keys from a KMS, rotate on schedule, and implement envelope encryption for payloads and attachments. Record key IDs in audit logs.

Validate address-to-chart mappings before writing to the EHR to prevent misassociation. Reject or quarantine when mappings are ambiguous and alert the owning team.

Send PHI-safe test messages hourly through MX, parsing, and webhooks and verify receipt in downstream systems. Alert on latency or loss outside SLOs.

Track MX accept rates, TLS handshake errors, MIME parse failures, webhook latency, and DLQ counts. Set thresholds aligned to clinical urgency.

Create alerts for spikes in DMARC failures, sender allowlist misses, and quarantine growth. Investigate quickly to prevent message backlogs.

Require two reviewers for release decisions and record approvals, message hashes, and timestamps. Prevents single-actor errors and strengthens audit posture.

Use tamper-evident storage with NTP-synchronized clocks and include IPs, cert fingerprints, and policy decisions. Retain per regulatory and legal-hold requirements.

Ship SMTP, parsing, and webhook events to the SIEM and automate triage playbooks. Correlate trace IDs across systems for rapid investigations.

Test MX failover, DNS rollback, webhook outage handling, and DLP false positive resolution. Capture lessons learned and update runbooks and thresholds.