Recently I have found a difference between Thunderbird 68 and 78 as follows: Suppose that I have a mail folder (mbox format under Dovecot server, although I could also see the same issue under other mail server such as Microsoft Exchange server / IMAP4): folder01/ folder01/folder02/ folder01/folder02/mail01 These folders are not being subscribed (ie. not listed under ".subscriptions" file). Under Thunderbird 68, when I choose "Subscribe..." under the mail account (appeared at the left side panel), "folder list" would have "folder01" listed, but having all subfolders not shown (ie. collapsed: without showing folder02, and mail01). Under Thunderbird 78, when I do the same, folder list would have all folders and subfolders showed (all expanded by default: folder01, folder02, mail01) I would like to know if there are options under Thunderbird 78 which could allow the behaviour of Thunderbird 68. One of our users has found this out and he is very unhappy with this default under Thunderbird 78. Thanks.