Sends an email from a template, right away unless you pass scheduledAt. You only need read access to the template.

Template variables are filled in from the first to recipient's contact, your name, signature and calendar link, and then the variables you pass, which take precedence. If any variable is left without a value the email is not sent and you get 400 with their names. Tracking and CRM logging follow your Mixmax settings unless you set them here. If you leave out cc or bcc, the template's own cc and bcc are used.

The response has no body, so it does not return the new message's id. To find it, list your messages with GET /v1/messages.