Email Infrastructure Checklist for Customer Support Teams

Use subdomains like support.example.com and billing.example.com with separate MX records to isolate traffic and simplify routing policies by team. This separation improves deliverability and makes per-queue metrics unambiguous.

Publish at least two MX records with correct priorities and geographically diverse endpoints. Validate failover by pausing the primary and confirming SMTP handoff to the secondary without message loss.

Authorize your inbound MX relays and any forwarding services in SPF to avoid misclassification when messages are redirected into your pipeline. Re-test after vendor changes or IP rotations.

Publish DKIM keys for each support-sending identity to reduce spoofing and help with threading consistency. Rotate keys annually and ensure selectors are documented for incident response.

Start with p=none and rua/ ruf reporting, then move to quarantine or reject after monitoring alignment. Tune pct gradually to avoid blocking legitimate forwards used by customers.

Route unknown addresses on the support domain to a quarantine mailbox rather than dropping them. Review weekly to identify typos that need aliases or auto-responses.

Require STARTTLS to your MX and monitor for plaintext downgrade attempts. Keep ciphers and protocols current and alert on certificate expiration within 30 days.

Use IP allowlists and SMTP auth for known forwarders or gateways that inject mail into your API. Audit logs monthly to catch unexpected sources that could create spam tickets.

Run AV/AM scanning and block executables, then quarantine suspicious files and cap total message size to protect agents. Provide a secure file upload link in auto-replies for oversized content.

Define patterns for card numbers, SSNs, and secrets, then redact before storing or indexing while keeping a secure audit copy. Log redaction events for compliance reporting.

If enterprise customers encrypt mail, integrate decryption keys and automate trust store management. Fail closed with a clear bounce or auto-response when decryption is impossible.

Inspect Auto-Submitted and Precedence headers and common templates to avoid ticket storms. Suppress SLA clocks for machine-generated messages and tag them for reporting.

Normalize to UTF-8, prefer text/plain when available, and sanitize HTML to remove scripts and trackers. Preserve minimal styling for agent readability without risking XSS.

Capture Message-ID, In-Reply-To, and References for threading accuracy. Store these fields alongside ticket metadata to reduce duplicate tickets and improve merge confidence.

Map Content-ID references to inline display while separately storing file attachments with MIME types. Enforce per-file and total attachment limits to keep queues performant.

Use the earliest trusted Received header for SLA start and convert to UTC for analytics. Keep both original and normalized times for audits.

Identify delivery status notifications and non-delivery reports to avoid ticket creation loops. Link DSNs back to the originating ticket when relevant for outbound replies.

Run lightweight NLP to tag urgency, sentiment, and product areas, then feed these signals into routing rules. Use confidence thresholds to prevent misroutes.

Use Message-ID hashes or a custom external-id to prevent duplicates within a 48-hour window. Store idempotency keys and return 2xx on replay to keep webhooks fast.

Route based on mailbox, customer tier, and detected intent, and attach the correct SLA policy at ingest. Start the clock from normalized receipt time.

Maintain a list of high-value domains and accounts that trigger priority routing or on-call notify. Audit quarterly to ensure coverage of strategic customers.

Integrate schedules and business hours to distribute tickets only to available agents. Fallback to team-level queues outside coverage windows.

Automatically merge when In-Reply-To or References match an existing ticket, and block creation if the subject-only duplicates within a short interval. Provide an override for edge cases.

Use Delivered-To and X-Original-To to tag tickets by mailbox like support@ or billing@ for clear reporting. Enforce tags in routing rules to preserve queue integrity.

Use HMAC signatures with rotated secrets to authenticate inbound webhooks from your email gateway. Reject requests without valid timestamps or signatures.

Return non-2xx codes on transient failures and support multiple retry windows with jitter. Route exhausted events to a dead-letter queue for manual review.

Validate required fields like requester, subject, and body before insertion and reject malformed MIME parts. Log mapping errors with correlation IDs for quick debugging.

Store the unmodified message source with retention and access controls for audits and reprocessing. Link the archive record to each ticket for traceability.

When webhooks are unavailable, support time-bounded REST polling with cursors to avoid gaps. Throttle clients to respect rate limits and maintain fairness.

Set per-tenant and global limits to protect downstream systems during spikes. Implement queue depth alerts and surge buffers for seasonal peaks.

Send scheduled test messages with varied encodings, large attachments, and deep replies into every mailbox. Validate that tickets are created, routed, and threaded correctly.

Track MX response times, 4xx/5xx rates, and TLS handshake failures with alert thresholds. Include certificate expiry and DNS change detection in the same dashboard.

Define an SLO from SMTP receipt to ticket creation and alert when it exceeds target percentiles. Break down by mailbox and attachment size to isolate bottlenecks.

Build views for volume by mailbox, queue age, SLA breaches, and dedup rate so managers can act quickly. Share weekly digests with trend deltas and incident notes.

When MIME parsing fails, store samples with redacted content and actionable error codes. Create a triage workflow to reprocess after fixes and prevent recurrence.

Analyze rua data to spot alignment gaps and spoofing attempts that could harm support inbox trust. Adjust SPF/DKIM and third-party senders accordingly.