If Hosnieh Rafiee's statement "I have started a completely new message. So the header of my message was quite new and not carry any information for the old thread." is correct and if his delivered post contained In-Reply-To: and References: headers referencing the old thread, I can only imagine that perhaps his own MUA was responsible in some way or possibly some non-Mailman process or Mailman modification is involved on the Mailman host that added them, but I'm certain that standard Mailman does not. My take on a statement like that (with a result that it threads under some other message) was that the poster took an unrelated message, and
On 10/27/14, 6:01 PM, Mark Sapiro wrote: pressed "Reply" to get the list address in the To: line, and then deleted everything, and is just assume that be deleting the message and changing the subject that "of course" the system should know it is a new message. I have seen this done many times by people who will claim they started a new message (and many time it still contain the old message because their system hid quoted message almost completely from them).
-- Richard Damon