HTML templates are now supported for batch sending transactional email

You can now use your unique HTML code and edit it when sending transactional messages in batches.
Just edit the variable htmlContent for each message version you want to create.

Read here the full guide

{
   "sender":{
      "email":"sendinblue@sendinblue.com",
      "name":"Sendinblue"
   },
   "subject":"This is my default subject line",
   "htmlContent":"<!DOCTYPE html><html><body><h1>My First Heading</h1><p>My first paragraph.</p></body></html>",
   "messageVersions":[
     //Definition for Message Version 1 
     {
         "to":[
            {
               "email":"bob@example.com",
               "name":"Bob Anderson"
            },
            {
               "email":"anne@example.com",
               "name":"Anne Smith"
            }
         ],
         "htmlContent":"<!DOCTYPE html><html><body><h1>Modified header!</h1><p>This is still a paragraph</p></body></html>",
         "subject":"We are happy to be working with you"
      },
     
     // Definition for Message Version 2
      {
         "to":[
            {
               "email":"jim@example.com",
               "name":"Jim Stevens"
            },
            {
               "email":"mark@example.com",
               "name":"Mark Payton"
            },
            {
               "email":"andrea@example.com",
               "name":"Andrea Wallace"
            }
         ]
      }
   ]
}