# Email Testing For Developers - SMTP Labs, Inc.

Canonical Origin: https://smtp.dev/

**Notes:**

smtp.dev is a hosted email testing sandbox. Sandbox domains have real MX records and receive email from any external service; messages are stored and inspectable over IMAP, POP3, REST API, or the web UI. Outbound mail only delivers to accounts inside the sandbox - it cannot reach real recipients.

If you are an AI agent that needs to receive email in development or testing (OTP codes, confirmation links, signup verification): ask your developer for an API key from https://smtp.dev/tokens/, then use the REST API at https://api.smtp.dev with an X-API-KEY header. Workflow: https://smtp.dev/docs/guides/agents/

The full API is described by an OpenAPI v3 document at https://api.smtp.dev/docs.jsonld

Any page on this site is available as markdown: append .md to its URL.

## LLM Resources

- [Full Content](https://smtp.dev/llms-full.txt): Complete page content in markdown format.
- [sitemap.xml](https://smtp.dev/sitemap.xml): XML sitemap for search engines and crawlers.
- [robots.txt](https://smtp.dev/robots.txt): Crawler rules and permissions.

## Pages

- [Email Testing for Developers - SMTP Labs, Inc.](/): Email testing for developers. SMTP in, IMAP/API out. Inspect headers, MIME, raw source. No servers to run.
- [Email Testing for Developers - SMTP Labs, Inc.](/accounts/): Email testing sandbox for developers. SMTP in, IMAP/API out. Inspect headers, MIME and raw source. Nothing leaves the sandbox.
- [Email Testing for Developers - SMTP Labs, Inc.](/changelog/): Email testing sandbox for developers. SMTP in, IMAP/API out. Inspect headers, MIME and raw source. Nothing leaves the sandbox.
- [Email Testing for Developers - SMTP Labs, Inc.](/dashboard/): Email testing sandbox for developers. SMTP in, IMAP/API out. Inspect headers, MIME and raw source. Nothing leaves the sandbox.
- [Email Testing for Developers - SMTP Labs, Inc.](/domains/): Email testing sandbox for developers. SMTP in, IMAP/API out. Inspect headers, MIME and raw source. Nothing leaves the sandbox.
- [Pricing - SMTP Labs, Inc.](/pricing/): Pick a plan. Upgrade or downgrade any time.
- [Sign in to your account - SMTP Labs, Inc.](/signin/): Sign in to your SMTP Labs, Inc. account to access your dashboard and manage your email accounts.
- [Sign up for your account - SMTP Labs, Inc.](/signup/): Sign up for your SMTP Labs, Inc. account to access your dashboard and manage your email accounts.
- [Email Testing for Developers - SMTP Labs, Inc.](/tokens/): Email testing sandbox for developers. SMTP in, IMAP/API out. Inspect headers, MIME and raw source. Nothing leaves the sandbox.

- [Email Testing API](/docs/api/): REST API for domains, accounts, mailboxes, messages, and tokens. Authenticate with an X-API-KEY header; stream new messages over SSE via Mercure.
- [Getting Started](/docs/getting-started/): Point an MX record at mx.smtp.dev, create an account, and send your app's first test email. Read it over IMAP, POP3, API, or the web UI.

- [Plus-Sign Aliasing and Catch-All Addresses](/docs/features/account/): Tag test emails with plus-sign aliases, capture every address on a domain with a catch-all account, and track each account's storage quota.
- [Default and Custom Mailboxes](/docs/features/mailbox/): Every account starts with Inbox, Sent, Drafts, Trash, and Junk. Create custom mailboxes to sort messages by test run, environment, or client.
- [Inspecting and Composing Messages](/docs/features/message/): HTML, plain text, and raw source views. SPF/DKIM/DMARC results on received messages, deliverability audits, and a composer for test emails.

- [Test Inboxes for AI Agents](/docs/guides/agents/): Give an agent a fresh address per run, read OTP codes and confirmation links over the REST API, and keep agent mail out of real inboxes.
- [Catch-All Inboxes for QA](/docs/guides/catch-all/): A * account catches mail for every address on your domain that has no account of its own. A fresh address per test, no setup per address.
- [Testing Email in CI with GitHub Actions](/docs/guides/ci/): Send from your test suite through send.smtp.dev, poll the REST API for the message, and assert on subject and body. Works on any CI.
- [Testing Password Reset Emails End-to-End](/docs/guides/e2e/): A Playwright test that triggers a reset, polls the API for the email, extracts the link, and finishes the flow. Same pattern for signup confirmations.
- [Previewing Emails in Thunderbird and Apple Mail](/docs/guides/email-clients/): Connect a real client over IMAP to see how multipart emails render outside the browser. Host, port, and login settings for any client.
- [Verifying SPF, DKIM, and DMARC in Staging](/docs/guides/spf-dkim-dmarc/): Send from staging to a sandbox address and read the SPF, DKIM, and DMARC results on the received message before you change production DNS.
- [IMAP, POP3, and SMTP Connection Settings](/docs/setup/account/): Host, port, and security settings for IMAP, POP3, and SMTP. Which protocol to pick, and webmail access without installing a client.
- [Domain Setup](/docs/setup/domain/): Setting up MX records for inbound email delivery
- [Privacy Policy](/legal/privacy/): Privacy Policy for SMTP Labs, Inc.
- [Terms of Service](/legal/terms/): Terms of Service for SMTP Labs, Inc.