What is the best way to send an inline attachment?

@ritulg, there are some errors in your request:

1st: Send only content_id, you don’t need id in the parameters
2nd: Your content_type is wrong. It’s not img/png, it’s image/png
3rd: Your content must be base64
4th: content_disposition is not supported by Microsoft (in my requests, I don’t send it).

Hope this can help you.