You need to add the send mail token to authenticate your API requests. This is a unique token you can generate in your Agent within your ZeptoMail account. Use the send mail token as a header when you call ZeptoMail REST Email Sending API.
POST /v1.1/email
Query String:
POST
HOST: https://api.zeptomail.com
Header:
Authorization: zoho-enczapikey <space> <send mail token>