post https://api.servicem8.com/platform_service_email
When you send an email using the Messaging API, the email signature of the current user is automatically appended to the message.
Note: you must supply one of htmlBody or textBody in order to send a message, or you may specify
both parameters. If you don't have a HTML-formatted or text-formatted version available, then simply
supply the version that you do have and omit the other parameter. Submitting an empty string
for either htmlBody or textBody will result in messages that cannot be viewed on some email clients.
You may specify a Reply To address, but the From address is controlled by ServiceM8.