A reason for threading errors in Mail.app

[Alex Tweedly]

Dennis Brown wrote:

> Dan and Mac Mail.app users and anyone who replies to messages,
>
> I have noticed that Mail.app seems to put seemingly unrelated threads  
> into an existing thread at times.  I think I see a possible  
> explanation for this.  In addition to the usual method of looking at  
> the subject text, I think mail.app also fingerprints messages  
> somehow, so it knows when a reply is to that message --even if the  
> subject line is altered.  So if somebody starts a new thread by  
> replying to a thread I started or replied to, just to get the header  
> info, then replaces the body and subject lines to a new topic, my  
> Mail.app assumes it is still related to the original message.  I just  
> tested out this theory by replying to a thread I started, but I  
> changed everything about the message except the To: line.  Sure  
> enough the message came back threaded to the unrelated message I  
> started it from.
>
That seems likely - though it's not particularly the mail.app - it's 
been part of the mail standard for 20+ years.

The headers for the mail I'm replying to included the following lines:

Message-id: <86EB8A37-219C-4ED8-8688-559546E8A57E at writeme.com>
In-reply-to: <C100E526-7D76-46EF-BD07-0CA31544B0CD at danshafer.com>

and these are used (probably along with others) to decide what's a 
thread and what isn't. 
(See rfc 822 published in 1982 !!)

> A case of too smart for its own good!
>
A case of doing exactly what the standard says it should do.


-- 
Alex Tweedly       http://www.tweedly.net



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