... now I know! TB2 must have been threading them based on subject line, and TB3 isn't (or there's a setting that's changed). TB3 has also lost the very useful shortcut Ctrl-Shift-C to mark a whole folder as read. I'm beginning to wonder why I upgraded Cheers posted: 11 Mar 2010 22:21 from: Paul Boyd Ah-ha! There are some settings in the config file that have changed defaults. If anyone else is interested, the following need to be changed: mail.correct_threading false mail.strict_threading false mail.thread_without_re true This puts threading in Thunderbird 3 back the way it was in TB2. The first post is still unthreaded though! posted: 11 Mar 2010 22:51 from: Martin Wynne Paul Boyd wrote: The first post is still unthreaded though! Hi Paul, The probable reason is that the "re:" part on replies is not the first thing on the subject line: First post subject line: [Templot Club] How many fish in a kettle? Reply subject lines: [Templot Club] ...