On 9/1/2013 3:10 PM, R. David Murray wrote:
This doesn't work, though, because you could (although you usually won't) have more than one 'text/html' part in a single multipart.
I was traveling and your original message is still unread in my queue of "things to look at later" :( I haven't caught up with old stuff yet, but am trying to stay current on current stuff...
The quoted issue was mentioned in another message in this thread, though in different terms.
I recall being surprised when first seeing messages generated by Apple Mail software, that are multipart/related, having a sequence of intermixed text/plain and image/jpeg parts. This is apparently how Apple Mail generates messages that have inline pictures, without resorting to use of HTML mail. Other email clients handle this relatively better or worse, depending on the expectations of their authors! Several of them treat all the parts after the initial text/html part as attachments; some of them display inline attachments if they are text/html or image/jpeg and others do not. I can't say for sure if there are other ways they are treated; I rather imagine that Apple Mail displays the whole message with interspersed pictures quite effectively, without annoying the user with attachment "markup", but I'm not an Apple Mail user so I couldn't say for sure.
You should, of course, ensure that it is possible to create such a message.
Whether Apple Mail does that with other embedded image/* formats, or with other text/* formats, or other non-image, non-text formats, I couldn't say. I did attempt to determine if it was non-standard usage: it is certainly non-common usage, but I found nothing in the email/MIME RFCs that precludes such usage.