Guides

Practical, developer-first guides to transactional email and getting it reliably into the inbox.

Transactional email: what it is, the types, and how it's sent

A developer's guide to transactional email: what it is, how it differs from marketing email, the common types (password resets, receipts, OTPs), how it's sent over SMTP vs an API, and how to keep it out of spam.

Deliverability

Email authentication: SPF, DKIM, DMARC, and BIMI

How email authentication works and how to set it up. SPF, DKIM, DMARC, and BIMI explained plainly — with the records you need, the Gmail and Yahoo sender requirements, and free generators for each.

Deliverability

Why your emails go to spam — and how to fix it

A practical checklist for transactional email landing in spam: missing SPF/DKIM/DMARC, sender reputation, content triggers, missing unsubscribe headers, bounces, and more — each with the fix.

Deliverability

One-click unsubscribe and the List-Unsubscribe header (RFC 8058)

How the List-Unsubscribe and List-Unsubscribe-Post headers work, what RFC 8058 one-click unsubscribe requires, why Gmail and Yahoo now mandate it for bulk senders, and how to implement it correctly.

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