# Inboxes

Create a deterministic address and keep each test run separate.

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## Register before sending

Use the [first-email recipe](https://www.inboxspec.com/docs/markdown/first-email.md) to register a deterministic inbox and keep its returned address. Guessing an address does not register it. The API key and inbox must belong to the same project.

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## Isolate each test run

Give each independent journey a fresh run ID. For repeatable suites, [fixture manifests](https://www.inboxspec.com/docs/markdown/fixtures.md) provision named inboxes and detect drift without clearing existing mail.

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## Inspect and clean up

Watch arrivals under Project → Inboxes in the console. Read full message content with a project-authenticated client. After producers and waits finish, clean up the exact run or let its configured retention expire.