Email Infrastructure Checklist for E-commerce

Create dedicated subdomains like orders@inbound.yourstore.com, vendors@inbound.yourstore.com, and returns@inbound.yourstore.com so pipelines can be independently scaled and monitored.

Model expected SMTP concurrency and message size distributions for promotions and holiday spikes, then size workers and queues to handle 10x baseline without latency.

Standardize fields like order_id, vendor_id, sku, quantity, currency, and message_id to reduce downstream branching and speed up new vendor integrations.

Store original MIME with checksums and encryption for auditability and reprocessing, and set retention aligned with chargeback windows and legal hold requirements.

Use RFC 822 Message-ID and a stable vendor fingerprint to prevent duplicate orders when emails are retried, forwarded, or resent by vendors.

Plan for HMAC-signed webhooks, IP allowlists, and role-based access for viewing raw messages containing PII to meet privacy obligations.

Point MX for inbound.yourstore.com to highly available SMTP endpoints with low TTL for quick failover, and validate delivery with test messages from key vendors.

Require STARTTLS for vendor connections where possible, and log negotiated ciphers to detect weak client configurations that may need exceptions.

Accept addresses like orders+acme@inbound.yourstore.com to route emails by vendor, easing onboarding and enabling per-vendor throughput limits.

Validate vendor authenticity and flag spoofed purchase orders by enforcing DMARC policy and scoring SPF or DKIM results in message metadata.

Route DSNs and NDRs to a special mailbox and parse status codes to identify vendor delivery issues and misrouted replies that impact order timelines.

Use a warm standby MX with queueing to absorb traffic during primary outages, and test failover monthly with controlled vendor emails.

Prefer text/plain over text/html when both are present, sanitize HTML tables when needed, and annotate the chosen part for reproducible parsing.

Handle quoted-printable, base64, and charsets like ISO-8859-1 from older ERPs, and convert to UTF-8 to avoid SKU or customer name corruption.

Store attachments with content-type, size, and SHA-256 hash, scan for malware, and prioritize structured CSV or XML over PDFs for line item parsing.

Create templates for common vendor formats like HTML order tables or CSV manifests, and use OCR as a fallback for PDF-only purchase orders.

Extract order_id, line items, quantities, shipping method, promised date, and vendor references, and tag confidence scores for downstream review.

Use In-Reply-To and References headers to associate return approvals or changes with the original order email, preventing duplicate tickets or shipments.

Include timestamped signatures, reject skewed timestamps, and rotate keys without downtime to secure order creation and RMA automation endpoints.

Use a deterministic idempotency key from Message-ID plus vendor_id to ensure repeated deliveries never create duplicate orders or returns.

Retry 409 and 5xx responses with jitter and route permanently failing messages to a review queue with the raw MIME for quick manual resolution.

Expose cursor-based retrieval for messages and parsed artifacts so marketplace operators can backfill when webhooks are disabled during maintenance.

Resolve SKUs to internal product IDs, apply vendor-specific quantity conversions, and flag mismatches for human review before order acknowledgment.

Parse return request emails to auto-create RMAs, allocate prepaid labels, and notify fulfillment with the original message attached for context.

Capture real order and PO emails from top vendors, anonymize PII, and use them as regression tests for the parsing pipeline.

Simulate 10x bursts over 30 minutes and 2x soak for 24 hours to validate MX throughput, parser CPU, and webhook latency budgets.

Track time from SMTP accept to order created, set per-vendor SLOs, and page on sustained breaches with enriched logs containing message_id.

Set thresholds for parse failure rates and automatically disable auto-fulfillment for vendors exceeding them until templates are updated.

Encrypt raw MIME and parsed fields at rest, redact email addresses and phone numbers in logs, and restrict access to least privilege roles.

Align raw email and artifact retention with payment dispute periods, configure automated purges, and support legal holds for investigations.