Most of my work-related mail goes through a ticketing system. Whenever a customer or me or any of my colleagues sends a mail or replies to a mail, the ticketing system sends a copy of said message to my inbox.
When 'threading' or 'sort on conversation' was on in Snow Leopard's Mail.app, it used to group all mail with the same subject. This way I could easily spot when a ticket was not yet replied to be my or one of my colleagues.
Lion's mail.app seems to behave differently and seems to sort mail by Sender rather than Subject. Does anyone know of a way to make Lion sort conversations by subject rather than sender?
Right now it's very annoying:

You would expect all mails with subject test to be grouped together, but they aren't. I would expect that it respects the "In-Reply-To" header.
These are the relevant headers of the first mail with subject [#VZB-74211-323] test:
Message-Id: <[email protected]> Second mail:
Message-Id: <[email protected]> In-Reply-To: <[email protected]> third:
Message-Id: <[email protected]> In-Reply-To: <[email protected]> fourth:
Message-Id: <[email protected]> In-Reply-To: <[email protected]> Surely there MUST be a hack somewhere or some plist to edit to fix this?

