How to get Mail to separate 2 threads that have the same subject

Question

I'm using Mail to view my IMAP account (Gmail).
"Organize by Thread" works, but it seems to be based only on subject, so old conversations started with the same subject as a new conversation show up together in the same thread.
This is particularly annoying for messages with no subject - there are hundreds of them all in the same thread.
Is there some way to tell Mail that a certain message is the start of a new thread?

Answer 1

Separating threaded messages into multiple threads, or combining messages into one thread, is defined in IAB [Internet Activities Board] Official Protocol Standards Network Working Group RFC [Request for Comments] 2822, proposed as a change to standard STD 11. Basically, the "References:" message header would be used for this purpose, as it would contain the unique message id's of all the precursor messages. See RFC 2822 at http://www.rfc-editor.org/rfc/rfc2822.txt for specific information. The current STD 11 has no detailed definition of the contents of this header.
Of course, email clients, including but not limited to Apple's 'Mail', must insert this optional header, properly populate it, and properly interpret it for threads to be defined in this way. However, it should be possible for the recipient's email client to insert and build or modify this header, with user guidance, so that conversational threads not originally identified can be documented or augmented. Valid arguments against changing existing headers should not really apply to the situation where the headers do not exist or where a reference is missing. These "Reference:" headers are in service to the users, not the network.
As stated, this is a proposed use of an optional header, and rules are advisory rather than mandatory. but definition of multiple parent emails at any point in the conversation is strongly advised against. Logical rules for identifying the thread break down if the chain of precursors forks when looking backward.
The above may explain Apple's mention of using headers to define threads, but the capability does not seem to have been implemented. How do we encourage Apple to move on this?