Email Deliverability Checklist for Customer Support Teams

Route all service mail to a dedicated subdomain with MX records pointing to your intake service. Use short TTLs so you can roll out changes without downtime.

Outbound acknowledgments and status updates must pass SPF to avoid customer mailbox rejection. Include helpdesk IPs and your ESP while keeping total DNS lookups under 10.

Sign all outbound support notifications so replies are less likely to be filtered by strict domains. Rotate selectors every 6 to 12 months and monitor for key acceptance.

Start with p=none to gather rua data, then move to quarantine or reject for the support subdomain. This reduces spoofing that confuses customers and agents.

Use MTA STS to encourage encrypted delivery and TLS RPT to detect failures. This reduces intermittent delivery issues caused by opportunistic TLS mismatches.

Deploy at least two MX targets on separate networks with priority values set correctly. Monitor with synthetic transactions so you catch degradation before it affects SLAs.

Segment addresses by product, region, language, or entitlement, and tie each to queue specific timers. This ensures accurate SLA tracking and clearer triage.

Embed ticket IDs in recipient aliases so replies map to the correct thread. Parse the alias server side to enforce reliable conversation linking.

If you forward mail from legacy inboxes into the intake, implement Sender Rewriting Scheme to prevent DMARC rejections. Test with strict senders like banks and public sector domains.

Set size limits and block risky file types before webhook delivery to protect queue capacity. Provide customers a secure upload link for large diagnostics.

Allow partner domains that send logs and block known spam sources at MX or gateway. Version the lists and review monthly with support leadership.

Throttle bursts from automated systems and return 4xx to trigger retries instead of drops. Protects agent capacity during incidents and launch days.

Normalize text, HTML, and attachments so agents see a clean view. Decode quoted printable and base64 to prevent unreadable tickets.

Strip scripts, tracking beacons, and unsafe attributes while preserving tables and inline styles common in receipts. Prevent cross site scripting in agent tools.

Use Message ID, In Reply To, and References headers to group replies. Fall back to subject and sender heuristics only when headers are missing.

Inspect Auto Submitted, Precedence, and List headers to identify vacation replies and list traffic. Tag them and mute escalation rules accordingly.

Use signature delimiters and reply markers to trim long threads while keeping a raw copy. Improves agent focus on the latest customer request.

Hash sender, subject, and a canonicalized body to merge near duplicate tickets within a short window. Reduces duplicate cases from customer retries.

Require signed payloads and rotate secrets on a set cadence. Reject mismatches with 401 and alert security to prevent forged intake.

Use event IDs or message digests to ensure a single ticket is created per message. Return 2xx only after persistence to the helpdesk is successful.

Store the original message and attachments so you can re parse when rules or mappings evolve. This supports audits, training data, and dispute resolution.

Populate custom fields for product, entitlement, and priority from headers or keywords. Drive automations that set assignees and due times automatically.

Run lightweight NLP on subject and body to flag urgent or churn risk messages. Route high negative sentiment to senior agents with tighter timers.

If webhooks fail, poll the intake API for undelivered messages and reconcile by ID. This prevents message loss during maintenance or outages.

Send regular test messages from major consumer and corporate providers to validate end to end intake. Track time from SMTP receipt to ticket creation.

Expose queue depth, parse errors, retry rates, and non 2xx responses. Alert when thresholds threaten response time commitments.

Review rua and TLS RPT for spikes, policy failures, and misconfigurations. Investigate any correlation with declines in ticket volume.

Validate PDFs, Office files, ZIP archives, and uncommon charsets from international customers. Confirm antivirus scanning and size limits behave as intended.

Practice switching to a backup mailbox or queue and verify audit trails remain intact. Assign roles and measure recovery time to improve readiness.

Ensure emails and attachments that contain personal data are redacted or encrypted with defined retention windows. Align policies with regional privacy laws.