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

[Steven D'Aprano]

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. It is completely
unreasonable to insist that people using non-broken tools must change their
habits to support those with completely broken tools.

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.


> 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.

*shrug*

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.


> 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.

The fact is, even if nobody ever changed the subject line, sometimes
threading will be broken. I can't find the energy to care about something
which already only sometimes works.




-- 
Steven