I use some newsgroups which accept postings either via newsreaders or email. Under these circumstances, it's not surprising that messages don't always get connected together in threads. If the server doesn't add or process the necessary data to allow messages to be threaded, they will all appear as standalone messages and cannot be threaded. Is it possible the Proton system simply doesn't support or recognise threading? Formally, threading is best implemented by using message id data. ISTR that Thunderbird has an option to do threading based on the subject. You can imagine that this can be a little fragile given that message subjects can be changed ad hoc. But do you think threading by subject might be worth a try? http://kb.mozillazine.org/Stop_threading_by_subject Some alternative ideas here: https://askubuntu.com/questions/71339/email-threads-by-subject-in-thunderbird-just-as-in-gmail Horses for courses; neither Unified Folders nor Gmail Conversations suit my taste or needs.