---
title: Email Infrastructure Blog | SendHQ
description: Practical, evidence-backed writing about transactional email, deliverability, inbound email, domain authentication and agent email workflows.
canonical: https://sendhq.cc/blog
last-updated: 2026-09-24
---
# Email infrastructure, explained for builders

Operational guides for sending expected email, receiving replies, protecting reputation and giving agents constrained access.

- [How to Receive Email with Amazon SES: S3 and Lambda](https://sendhq.cc/blog/receive-email-amazon-ses-s3-lambda): Build a production-ready inbound email pipeline with Amazon SES, S3, and Lambda, including MIME safety, tenant routing, idempotency, retries, and threading. Read article →
- [Amazon SES Pricing Tiers Explained (July 2026)](https://sendhq.cc/blog/amazon-ses-pricing-tiers-2026): Amazon SES shifted from a simple a la carte model to tiered plans (Essentials, Pro, Enterprise) on July 21, 2026. Here is the cost breakdown and what it means for your transactional email budget. Read article →
- [DMARC p=none vs Quarantine vs Reject: An Operator's Guide](https://sendhq.cc/blog/dmarc-policy-p-none-quarantine-reject): Choosing the right DMARC policy is a balancing act between security and deliverability. Learn the safe rollout path from p=none to p=reject to prevent spoofing without blocking legitimate mail. Read article →
- [Idempotency Keys for Email APIs](https://sendhq.cc/blog/idempotency-keys-email-api): Prevent duplicate emails during network retries by implementing idempotency keys. Learn how to handle distributed system failures without spamming your users. Read article →
- [SPF Flattening: Fixing the 10-Lookup Limit](https://sendhq.cc/blog/spf-flattening-lookup-limit): Stop the 'permerror' caused by too many DNS lookups. Learn how SPF flattening works, why the 10-lookup limit exists, and how to resolve include chains for better deliverability. Read article →
- [Bounce vs Complaint: What Actually Hurts Deliverability](https://sendhq.cc/blog/bounce-vs-complaint-deliverability): Bounces are technical failures, but complaints are reputation killers. Learn how to handle both to keep your sending reputation intact and your emails landing in the inbox. Read article →
- [Designing Email Webhooks for At-Least-Once Delivery](https://sendhq.cc/blog/email-webhook-reliability-patterns): Learn how to build resilient webhook consumers for email events using retries, idempotency keys, and signature verification to ensure no delivery event is ever missed. Read article →
- [The Transactional Email Migration Playbook](https://sendhq.cc/blog/transactional-email-migration-playbook): Migrating transactional email providers without losing observability requires a phased approach: dual-sending, event parity mapping, and gradual DNS cutovers. Read article →
- [Why the Same 50,000 Emails Cost $5 or $66](https://sendhq.cc/blog/email-api-pricing-spread-explained): A deep dive into the pricing spread of email APIs. We analyze why the same 50k volume varies by 13x across providers and how to choose based on your engineering constraints. Read article →
- [SendGrid Free Plan Is Gone: A 30-Minute Migration Guide](https://sendhq.cc/blog/sendgrid-free-plan-migration): SendGrid's free tier is now a 60-day trial. Here is a technical guide for engineers to migrate their transactional email to a sustainable alternative without downtime. Read article →
- [Resend-Compatible Email APIs: What Compatibility Does Not Cover](https://sendhq.cc/blog/resend-compatible-email-apis): API compatibility allows you to switch providers without rewriting your code, but it does not migrate your reputation, DNS records, or deliverability history. Read article →
- [Transactional Email API Production Checklist](https://sendhq.cc/blog/transactional-email-api-production-checklist): A technical guide for engineers launching transactional email systems. Covers DNS verification, idempotency, error handling, and cost analysis for production readiness. Read article →
- [How to Give an AI Agent Safe Email Sending Access](https://sendhq.cc/blog/safe-email-access-for-ai-agents): Giving an AI agent an API key is a liability. Learn how to implement scoped credentials, approval boundaries, and idempotency to prevent agent-driven email disasters. Read article →