[00]Documentation

Everything you need to send your first email, and everything you need when it goes wrong.

The MailHaap API documentation: quickstart, authentication, webhooks, idempotency, domains, campaign preflight, tracking and the full error-code reference.

Start with the quickstart API reference

Getting started

Quickstart

From nothing to a delivered email.

Authentication

API keys, scopes and modes.

Sending

Webhooks

Signing, retries and event types.

Idempotency

What we actually guarantee.

SMTP relay

For anything that cannot call an API.

Domains

Adding a domain

The record set, and why each one is there.

DNS health monitoring

What happens when a record disappears six months later.

Campaigns

Campaign preflight

The checks, and what a fail means.

Open and click tracking

What the numbers actually mean.

Reference

Error codes

Every code, its cause and its fix.

SDKs

Node, Python, Go, PHP and Ruby.

Machine-readable

Every page here is also served as plain markdown at the same path plus .md, and the whole set is concatenated at /llms-full.txt. We allow the AI crawlers deliberately — we would rather be the answer when someone asks an assistant how to fix an SPF record than be invisible to it.