# Good to know - [Authentification](https://documentation.np6.com/api/referencegood-to-know/authentification.md): ## Authentification All requests to NP6 CM APIs must be authenticated using an API key provided by NP6. The API key must be included in the HTTP headers of each request using the following format: `x- - [Rate Limiting](https://documentation.np6.com/api/referencegood-to-know/rate-limiting.md): ## Rate Limiting To ensure optimal performance and protect our infrastructure, **NP6 APIs** enforce rate limits on incoming requests. These limits may vary depending on the type of account and the nat - [Email - Tracking](https://documentation.np6.com/api/referencegood-to-know/email-tracking.md): ## Email - Tracking You will find below the attributes to pass in the HTML content of your actions to active CM tracking. - [Managing attributes on URLS for campaigns:](https://documentation.np6.com/api/referencegood-to-know/managing-attributes-on-urls-for-campaigns:.md): ### Managing attributes on URLS for campaigns: - External link: **`tracking="Enabled" dataminingname="label_of_your_link"`** - Form NP6 link: **`href="your_form_identifier" tracking="Enabled" datamini - [Managing attributes on URLS for overload messages with "design" option :](https://documentation.np6.com/api/referencegood-to-know/managing-attributes-on-urls-for-overload-messages-with-%22design%22-option-:.md): ### Managing attributes on URLS for overload messages with "design" option : - External link: **`dataminingname="label_of_your_link"`** - Form NP6 link: **`href="your_form_identifier" dataminingname=" - [Management of tracking for a shipment with overload of HTML content for messages with "view" option:](https://documentation.np6.com/api/referencegood-to-know/management-of-tracking-for-a-shipment-with-overload-of-html-content-for-messages-with-%22view%22-option:.md): ### Management of tracking for a shipment with overload of HTML content for messages with "view" option: - External link: **`