Re: [Jmap] Attachments and composing more complex MIME structures

[Neil Jenkins <[e-mail]>]

On Wed, 9 Aug 2017, at 04:17 AM, Neil Jhaveri wrote:
> Yeah, the Apple Mail clients have a preference to avoid sending
> text/html, unless strictly necessary by the content:
> (A) A philosophical preference that text/plain be used whenever
>     possible,> since it results in a neater and more overall compact message, without> the redundancy of including both a text/html part with a text/plain
> fallback alternative part.

Compactness is good, but with JMAP you can just upload the HTML part and
have the server generate a plain part so you're not saving over-the-wire
data on your bandwidth-constrained mobile anymore. It would really only
be for the server-to-server transmission, and I doubt that it would make
a significant difference.
> (B) Broken implementations in the wild that caused various small
>     support> issues. The Apple clients did change once to always sending
> text/html if> there are images, but reverted it in a software update. For instance,> some Japanese cell phone carriers couldn’t properly handle
> messages sent> to an MMS bridge e-mail address if an image wasn’t a top-level
> MIME part.
Interesting. I wonder whether that system is still relevant today? Given
other clients *don't* (usually) generate the multipart/mixed format,
this would presumably be seeing a lot of issues with emails sent from
e.g. Gmail.
> How do other people here feel about the preference for text/plain?

I believe that battle has been fought and lost. You can generate clean,
minimal HTML and it's the one way to get reasonable font wrapping
everywhere on mobile, including when quoting replies.
> I agree, I’d like to see if the API can remain as-is, and we detail in> the spec how servers should construct MIME. I’d be happy to help with> this part.

That would be great. :)

> There is also the uglier case of "inlined attachments" that cannot be> properly referenced by HTML tags, e.g.:
> [plain text]
> [zip attachment]
> [more plain text]
> 
> I think the Apple clients are the only ones that even support
> this in the> UI and make a multipart/mixed message out of it, but I’m not sure.

I don't believe I've seen one of them in the wild. I am now curious to
know what our client would make of it!
>  Does anybody know if any other major clients offer this kind of UX?

I'm not aware of any.

Neil.