I am attempting to send a message via the SendMessage endpoint. The message has an attachment. While everything sends fine, the contentId that I set - rather the field is called contendid, which I assume is correct in the doc - is not respected.
The problem is that inline images in the email are referenced via their contentId by all mail providers - Yahoo included. If you do not maintain the content id as I send the message, then inline images will never display.
here is the json I am sending. Again, this all works fine other than the fact that the contentId is not actually