> Idempotency key: A unique value you send with a request so that retrying it doesn't repeat the action.

Source: https://vaartix.com/glossary/idempotency-key

[Email glossary](https://vaartix.com/glossary)

# Idempotency key

Email glossary

A unique value you send with a request so that retrying it doesn't repeat the action.

## How this affects you

Send an `Idempotency-Key` header with `POST /emails` and retrying after a timeout becomes safe: the same key with the same body within 24 hours returns the first email's ID and sends nothing. The same key with a different body returns `409 idempotency_conflict`. Use something tied to the event, such as `order-1042-receipt`.

## Learn more

-   [Idempotency](https://vaartix.com/docs/sending/idempotency/)

Related: [Webhook](https://vaartix.com/glossary/webhook)

**Vaartix is a transactional email API built in India.** SPF, DKIM and a return path on your domain are set up for you, and every feature is free during the private beta.

[Request early access](https://vaartix.com/#early-access)