# About the Mailjet's Email API

Hello and welcome to the Mailjet's Email API!

Mailjet APIs are built using [RESTful principles](http://en.wikipedia.org/wiki/Representational_State_Transfer), featuring clear and consistent resource-oriented URLs for easy integration. It uses standard HTTP methods like `GET`, `POST`, `PUT`, and `DELETE` to interact with resources, and returns structured [JSON](http://www.json.org/) for all requests and responses—including errors. Each API request is made over [HTTPS](https://en.wikipedia.org/wiki/HTTPS) to a versioned endpoint, ensuring secure and predictable communication. [HTTP status codes](/docs/email-api/email-api-overview/status-codes) are used to indicate the success or failure of requests, making error handling straightforward for developers.

Info
In the Mailjet API, all PUT requests behave like PATCH requests. The update will affect only the specified properties. The other properties of an existing resource will neither be modified, nor deleted. It also means that all non-mandatory properties can be omitted from your payload.

## Versioning

The Mailjet API is spread under 3 versions.

- [V3](/docs/email-api/send-api-v3/send-basic-email): This includes all REST API resources and one transactional API resource.
- [V3.1](/docs/email-api/send-api-v31/send-basic-email): A second transactional API which includes advanced error management.
- [V1](/docs/content-api/content-overview/content-overview): The Content API is under V1


#### Version Differences

One of the main differences between the V3 and V1 versions is a change in authentication:

- V3s are using basic authentication with your public and secret API keys.
- V1 leverages a token authentication.


The URL paths for every API resource can be found in the API reference under the respective resource name.

## Rate Limits

Mailjet APIs are under rate limits for the number of API calls allowed per API keys per second. If you reach a rate limit, our API will return a 429 HTTP error code.

Our transactional APIs (Email and SMS) are offering a high rate limit to accommodate the most demanding messaging needs of our clients. The rate limits for the rest of our Email and SMS APIs (excluding transactional API calls) are much lower, while still allowing a comfortable use of our API by even the most challenging use cases.

To help better deal with these rate limitations, we have put in place Bulk functionalities, helping you increase the quantity of actions you can do with a single call. These functionalities are available for transactional endpoints and contact management endpoints.

When using the Mailjet API, we recommend to:

- Properly take into account any 429 error (wait and retry)
- For high frequency use of our API resources, explore the use of our bulk functionalities
- Separate applications under separate sub accounts