Meaning and purpose of the Subject field (was: Ignore error with non-zero exit status)

[Jon Ribbens]

On 2015-12-21, Steven D'Aprano <steve at pearwood.info> wrote:
> On Tue, 22 Dec 2015 08:44 am, Jon Ribbens wrote about mail clients that use
> the Subject line to thread messages:
>> Also: Thunderbird, The Bat!, Eudora, Gnus, Outlook, Outlook Express,
>> Pegasus Mail, Pine, Apple Mail, Windows Live Mail, Yahoo Mail,
>> Evolution, SquirrelMail, KMail, Windows Mail, etc.
>
> I understand that at least some of those will only use the Subject as a
> fallback when other threading information is not available. That's a
> reasonable strategy to take.
>
> As for mail clients that *always* and *exclusively* use the subject
> line to implement threading, they are horrifically broken.

Yes, that would be bizarre and clearly wrong. Are there any such clients?
I wouldn't put it past Microsoft to do such a thing, of course ;-)

> So as far as I am concerned, if changes of subject line breaks
> threading for you, so sad, too bad. Go without threading or use a
> better mail client.

I have no comment on that.

> The whole purpose of the change of subject is to indicate in a human-visible
> way that the subject of the thread has changed, i.e. that it is a new
> thread derived from the old one. If that breaks threading, oh well, it
> breaks threading.

That sounds a bit confused - if the *intention* of changing the
subject line is to create a new thread, then breaking the thread
is not "breaking threading" ;-)

>> And, yes, fixing the mail clients of "everybody else in the world"
>> might be a lovely idea but it is a little impractical to implement.
>
> Less impractical than insisting that "everybody else in the world" must
> change their posting habits to suit those using broken mail clients.

Fortunately I haven't suggested that.