> For the complete documentation index, see [llms.txt](https://docs.emaillabs.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.emaillabs.io/en/email/email-api/settings/smtp-accounts/headers.md).

# Headers

'Headers' are a feature that allows you to add additional parameters to email messages, which are then passed to the recipient’s server. This helps mailbox providers like Gmail or Yahoo better understand the nature of the message and classify it accordingly, such as under “Primary,” “Social,” or “Promotions” tabs. Adding headers can improve deliverability and increase the likelihood that the message reaches the correct section of the recipient’s inbox.