Inbox
Inbox — engineering notes on transactional email.
SMTP, deliverability, DKIM/SPF, AWS SES playbooks, and post-mortems. Long-form pieces from the team running it in production.
Transactional Subdomain Strategy: Why mail. Beats the Apex
Sending transactional mail from your apex domain ties your inbox placement to every other system touching that name. A dedicated transactional subdomain isolates reputation, simplifies DKIM, and gives you a clean upgrade path.
TLS-RPT Setup: Aggregate Reports for SMTP TLS Failures
Publish a TLS-RPT TXT record and ingest the JSON aggregate reports that Gmail, Microsoft, and other receivers send. Spot MTA-STS and DANE failures before users do.
SMTP TLS vs STARTTLS: Port 465 or 587?
Implicit TLS on port 465 and STARTTLS on port 587 both encrypt SMTP, but they negotiate the session very differently. Here is how each handshake works and which one a transactional sender should pick.
Webhook Idempotency: Surviving Retries and Duplicates
Providers retry webhooks on any hiccup, so your receiver must treat every delivery as possibly duplicate. Here is the verify, dedupe, and ack pattern that survives.
IP Warmup Schedule: A 30-Day Ramp for New Sending IPs
A concrete 30-day IP warmup schedule with daily volume caps, per-ISP throttling tactics, and the bounce/complaint metrics that tell you when to push or pull back.
Dedicated IP for Transactional Email: When It's Worth It
A dedicated IP is the right move for some senders and a deliverability hazard for others. Here is the volume math, the warm-up cost, and the modern domain-reputation context that decides it.
SMTP vs REST API for Transactional Email: When Each Wins
SMTP wins on universal client compatibility and zero-SDK integration. REST wins on latency, structured errors, and analytics attribution. Pick by use case, not dogma.
Magic Link vs OTP: Passwordless Email Auth Trade-offs
Magic links and one-time codes both kill the password, but they fail in different places. Pick the wrong one and you lose users on a phone-to-laptop handoff or burn deliverability on a clickable token.
Email Bounce Handling: Hard, Soft, and Suppression Lists
Bounces are signal, not noise. Classify them with SMTP codes, persist them in a suppression list, and stop sending to dead addresses before mailbox providers downgrade your reputation.
BIMI Record Explained: Brand Logos in the Inbox
BIMI puts your verified logo next to authenticated mail in supporting inboxes. Here is how the DNS record, SVG, and VMC fit together — and when the cost is worth it.
SPF Record Syntax Explained for Senders
A field guide to the SPF record: every mechanism, every qualifier, the breakage modes that quietly kill deliverability, and the dig command to verify your work.
DMARC Policy: Quarantine vs Reject (When to Advance)
A practical rollout guide for moving a DMARC policy from monitoring to enforcement without losing legitimate mail along the way.
Stop Using Your Marketing Email Platform for Transactional Mail
Marketing email platforms are built for campaigns, not time-sensitive one-to-one messages. Routing password resets and receipts through the same tool that sends your newsletter is the fastest way to lose both deliverability and sleep.
Configure DKIM for AWS SES (Step-by-Step Guide)
Enable Easy DKIM on AWS SES in about five minutes: three CNAME records, one CLI flag, and a dig check to confirm the keys propagated.