Transactional Email Deep Dive — Resend, SendGrid, and Deliverability

Your app needs to send email. Not marketing blasts — transactional email. The emails your users actually need: password resets, order confirmations, welcome messages, invoice receipts, security alerts. These are the emails that, if they don't arrive, your app feels broken.

You might think sending email is simple. It's not. Email is one of the oldest and most byzantine systems on the internet. Getting your emails reliably delivered to inboxes — not spam folders, not the void — requires understanding a stack of acronyms and choosing the right tools.

Let's make sense of it.

Transactional vs. Marketing Email

This distinction matters because they have different sending patterns, compliance rules, and often use different services:

| | Transactional | Marketing | |--|--------------|