> 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/s-mime.md). # S/MIME S/MIME (Secure/Multipurpose Internet Mail Extensions) is a cryptographic standard used for encrypting and signing email messages, ensuring both the security of the content and verification of the sender’s authenticity. With S/MIME, messages are protected from unauthorized access, and recipients can be assured that they originate from the correct sender. To use S/MIME, you need to purchase a digital certificate and provide it to us for configuration. This certificate will enable message encryption and the addition of a digital signature, significantly enhancing the security of email communication. For details regarding the cost of implementing an S/MIME certificate, please contact our Customer Support team at .