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

[Alexey Melnikov <[e-mail]>]

On 09/08/2017 09:03, Neil Jenkins wrote:

> On Tue, 8 Aug 2017, at 10:31 PM, Josef 'Jeff' Sipek wrote:
>> Is there a MIME-aware client that breaks with what the iOS client 
>> generates?
>
> I don't know; I haven't tested this exhaustively. I know we had bugs 
> with this multipart/mixed style at one point, since it was pretty 
> uncommon so I wouldn't be surprised if there were bugs or lack of 
> support elsewhere too.
I've spent some times implementing this in our client. We had some bugs, 
but it works nicely now. You had to implement this if you are a MIME 
capable email client.

> More importantly, plain text is deeply problematic on mobile because 
> of hard wrapping. Format=flowed has zero traction 
> <https://blog.fastmail.com/2016/12/17/format-flowed/>,
Let's not exaggerate. It is being used.

> so you mostly end up with hard wrapping that breaks in /really/ 
> awkward positions on many mobile screens, as it normally presumes you 
> can fit 80 chars in a single line.
>
>> In theory the multipart/mixed approach should be **more** compatible 
>> than HTML, since the client doesn't have to deal with HTML on top of 
>> dealing with MIME anyway.
>
> Maybe, but I wouldn't be surprised if the MIME handling in some 
> clients extended only to "find the right part to show".
>
>> As a mutt user that likes text/plain emails... it'd be great if these 
>> generated emails displayed nicely with non-HTML based MUAs. :)
>
> There's no reason why the server can't generate a reasonable textBody 
> component as well (it will have to do this as well as htmlBody in this 
> case anyway). I believe you could build an excellent plain-text only 
> client on JMAP if you wanted, although realistically all modern email 
> clients have to deal with HTML.

True.
>> Is the goal to make only the simplest of clients easy to implement? 
>> Where does one draw the line between simple enough to use the nice 
>> jmap interface and too complex (IOW: just implement the whole RFC 
>> 5322/MIME/etc. stack and use the blob API)?
>
> I believe you could implement the functionality of most modern GUI 
> email clients without resorting to MIME parsing. This is basically the 
> goal: most clients never need to deal with the raw message, but some 
> with support for less common features can do so if they want (like for 
> S/MIME). For example, I believe you could implement all the 
> functionality in the iOS/macOS Mail apps using the JMAP Message 
> object, although the implementation underneath might vary in some 
> aspects like the one we're discussing.  (Neil, do you agree?).
>