SMTP relay: what it is and how to set one up
An SMTP relay hands your app's mail on for it. What one is, when you need it, ports 465 and 587, the reply codes, and setup for six common clients.
Schedule email API: send at a time you choose
Schedule an email over the API: an ISO 8601 scheduled_at up to 30 days out, a PATCH to move it, a cancel, and the time-zone mistakes to avoid.
Email API rate limits: headers and backoff
Email API rate limits at Rasket: 10 requests a second per team, the four headers, a 429 retried with the same key, and the quotas that are not rate limits.
Email template variables done right
How email template variables should work: declared with a type and a fallback, checked at send, versioned so each email records what it said, and HTML-escaped.
Email API vs SMTP: which should you use?
SMTP is a conversation; an email API is one request. What each gives you on retries, idempotency, events and firewalls, and how to move from one to the other.
Idempotent email sends: never send twice
A timeout does not tell you whether the send happened. What an idempotency key is, how the 24-hour window behaves, how to choose keys, and what a batch does.
Transactional vs marketing email: how to send each
What separates transactional email from marketing email — the trigger, consent, unsubscribe headers and reputation — and how to send both from one API.
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