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Apollo Signal gives your application one place to send transactional email, authenticate sending domains, manage recipients, inspect delivery outcomes, and react to signed events. These guides cover the customer-visible workflows in the Signal dashboard and the public API.

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Start here

1

Create or select a project

A project is the boundary for API keys, domains, contacts, messages, webhooks, usage, and metrics. Choose the project region carefully because you cannot change it after creation.
2

Verify a sending domain

Add the domain used by your From address, publish the DNS records Signal provides, and wait for the domain to become verified.
3

Create a restricted API key

Create a key with only the permissions your integration needs. Copy the raw key when it appears because Signal does not show it again.
4

Send and inspect one message

Send to an address you control, then open Emails and follow the message timeline through delivery or failure.
5

Add operational feedback

Configure signed webhooks, review suppression handling, and monitor delivery, bounce, complaint, and quota signals.

Dashboard quickstart

Complete the same setup flow shown in the Signal dashboard.

Send with your stack

Install an official SDK for your language or use REST or SMTP.

API reference

Review request fields, permissions, status codes, and response schemas.

Webhook guide

Consume final delivery outcomes safely.

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Core boundaries

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Message lifecycle

The send response confirms acceptance, not inbox delivery. A message may move through queued or scheduled, then sent, delivered, opened, or clicked. It can instead become bounced, complained, failed, rejected, or suppressed. Use the email timeline and webhooks as the source of truth for asynchronous outcomes.
Never put a Signal API key in browser JavaScript, a mobile application, a public repository, or support output. Call Signal from infrastructure you control.