User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 1.1.4322) Build Identifier: This would mainly be of use to people that use mailing lists. Some of the time people start a new thread by replying to an existing post, rather than starting a new one. This then shows up in thunderbird as a reply to the original, as opposed to being in it's own thread. The ability to be able to select a message to break/split the thread so that the selected message is no longer displayed as part of the original thread, but at the top of it's own would be useful. Reproducible: Always Steps to Reproduce:

Very good idea!

(In reply to comment #0) What's even worse than mailing lists is when someone sends you messages with the same common subject, for instance "FYI" or even "" (no subject). I have about 5 of each in my inbox right now, and none of them are related.

I think converse action of this is important, too. I often want to merge threads. I submitted bug 295873. I guess that makes it "half-duplicate".

any progress at all on this?

I have also been bugged (no pun intended) by this for a long time. I have just uploaded my entire archive of e-mail to GMail, and I have one thread in there with subject "" that spans hundreds of unrelated people, and almost five years, that in fact _is_ unrelated! If I may make a suggestion: From my observations, TB threads the mails based on two criteria (remember, this is only MY observations, and may not reflect reality): based on the References or possibly In-Reply-To headers and the Subject. If I am correct, then ideal solution for me would be to create a boolean Preference (in the prefs.js), something like ignore.subject.threading that I could set to false, after which mail would only be threaded if it contains the correct References or possibly In-Reply-To headers.

I swear there's another bug on this. In the meantime, confirming this enhancement.

Yup, a real old one.

This request is about splitting, the one marked as the duplicate is about merging threads. It's a similar topic but not a duplicate.