Support for nested multipart body

[ktyborowski]

Postal has support for nested multipart content in the message body: example message from postal.

This is useful when one wants to send an alternative (html, text) body with attachments. It seems that the proper way to structure the message is to make the root multipart/mixed and then include a multipart/alternative part in it, which contains the html and text.

Is this supported in tarayo?