In article 4E319B13.8000000@hogranch.com, John R Pierce pierce@hogranch.com wrote:
On 07/28/11 8:52 AM, Karanbir Singh wrote:
the thing is that not all mail clients will set the in-reply-to headers, whuch is why clients like thunderbird, evolution and mutt will use the subject line as well to thread messages.
Its the "References:" header that controls threading in mail clients that support it. I'm using thunderbird, and afaik, it won't revert to Subject based pseudo threading in the absence of References. Subject line changes don't break the thread, which is why using 'reply' and changing the subject to start a new thread makes a mess wherre the new thread is buried in the original that it was in reply to....
References: is for Usenet news, not email. Email uses In-Reply-To.
In fact, on my local server, mail messages from the centos list are fed through a filter that changes In-Reply-To to References and then fed into my local INN news server, so I can read it with a threaded news reader instead of a mail program. The group is set to be moderated, so when I post, it gets emailed to the list address. Before doing so, it goes through another filter that changes the References: header back to an In-Reply-To with the mode recent message-ID.
Cheers Tony