Is there any plugin, setting or what ever that forces Mail.app to use
In-Reply-To header field when grouping messages to conversations?
My problem is that I'm a member of many mailing-lists that use subjects in form:
[Listname:1234] and the number changes with every message. This causes Mail.app to group messages by Sender, creating multiple conversations instead of one.
Mountain Lion's Thread view had it correct. Same goes for Sparrow which displays the same messages in single conversation.