User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.8) Gecko/20050511 Firefox/1.0.4 Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.8) Gecko/20050511 Firefox/1.0.4 Thunderbird can not do threads perfectly. Often, it is desirable to start a new thread even though it may have the same subject matter. Conversely, I often want to move a message into a thread even though Mozilla has sorted it separately. Reproducible: Always Steps to Reproduce: 1. Receive a message with a subject similar to an already received message 2. right click Actual Results: No "new thread" or "merge thread" option appears Expected Results: Should get a context menu with "add to old thread"/"start new thread" or "merge threads"/"split threads" options.

By default, Tb threads messages with the same subject like this, but a hidden preference can turn it off. Wiki entry: http://kb.mozillazine.org/Stop_threading_by_subject http://bugzilla.mozilla.org/show_bug.cgi?id=273497 http://bugzilla.mozilla.org/show_bug.cgi?id=164115 This bug should be marked as INVALID I believe, since it doesn't make much sense to continue sorting by subject, yet try to add additional information to split some of these messages into separate threads, and further, have to manually 'build' threads from all those messages. Imagine having 100 messages from 20 different conversations, all with the subject "Report" (or "Re: Report"). You'd have to manually link the messages of each of those threads together.

Agree on Invalid; this bug describes two related but separate features: splitting a message from a thread, and adding a message to a thread (bug 36024).