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

[Jon Ribbens]

On 2015-12-21, Ian Kelly <ian.g.kelly at gmail.com> wrote:
> On Mon, Dec 21, 2015 at 1:58 PM, Ben Finney <ben+python at benfinney.id.au> wrote:
>> Ian Kelly <ian.g.kelly at gmail.com> writes:
>>> This isn't just a Usenet group; it's also a mailing list, and many
>>> MUAs rely on the Subject header for proper threading.
>>
>> If such MUAs do that, they're misinterpreting the Subject field. Other
>> fields are available with the explicit meaning of relating messages to
>> each other regardless of what they discuss.
>>
>> If the correct fields are being mangled, then the correct place to apply
>> pressure is on those who can fix that error. Let's not overload the
>> Subject field to make up the lack.
>
> It might just be Gmail.
>
> http://webapps.stackexchange.com/questions/965/how-does-gmail-decide-to-thread-email-messages
>
> I can't specifically recall if I've used any MUA other than Gmail that
> even attempts threading email 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.

Trying to suggest that MUAs should never look at the Subject line for
threading is, unfortunately, ridiculous. Yes, in theory it shouldn't
be necessary but in practice enough people are using poor clients that
don't provide enough context in the proper headers that it can't be
avoided.

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.