Email / SMS Delivery — Notes

Functional

• Multi-channel send API.
• Templates + localization.
• Suppression / unsubscribe / bounce handling.
• DLR (Delivery Reports) ingest.
• Per-channel routing (region, carrier).

Non-functional

• p99 send < 2 s for txn.
• 99.9% delivery for valid recipients.
• Bursty (campaign sends).

Trade-offs

• One provider = simple but risk; multi-provider = failover + costlier ops.
• Throttle per carrier rate cards strictly.
• Reputation: warm IPs, SPF/DKIM/DMARC mandatory.

Refs

• Twilio architecture talks; SendGrid, Mailgun blogs.
• Postmark on transactional vs marketing.
• AWS SES, GCP Pub/Sub + email integrations.