User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.0.1) Gecko/20060111 Firefox/1.5.0.1 Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.0.1) Gecko/20060111 Firefox/1.5.0.1 Many people unknowingly reply to a message instead of choosing "new message" when starting a new topic or thread, meaning that message threading becomes useless. The fix is to manually run a filter on the message that rewrites (deletes) the References header. I call this the "Break Thread" tool. This could be added as a general-purpose rewrite header option for filtering (see KMail for example) or as a purpose-built feature. Reproducible: Always

Related to bug 259040, Core bug 36024, bug 279631 comment 1 and Core bug 141167 comment 19?

(In reply to comment #1) > Related to bug 259040, Core bug 36024, bug 279631 comment 1 and Core bug 141167 > comment 19? "Related" -- that's a tactful/polite way of saying, "a duplicate of bug 259040 ...". :-) Many thanks for IMO one of the very best mail agents and sorry I didn't catch the dupe before posting.

Bug 259040 doesn't mention filtering so this bugreport could also have been an enhancement request for bug 259040 (-> 'Bug 331342 depends on: 259040'), I wasn't sure. It seems that the TB Header Tools Extension 0.5.5 from http://forums.mozillazine.org/viewtopic.php?p=2090651#2090651 can change/rewrite message headers (see http://forums.mozillazine.org/viewtopic.php?t=279907).