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

[Ian Kelly]

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.