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The mail server for account responded: SUBSCRIBE failed." When I turn back on "Show only subscribed folders" the folders disappear again, and when I try to (re)subscribe to them, the activity manager shows errors reading "The current command did not succeed. I can see all the folders if I go into Server Settings->Advanced and uncheck "Show only subscribed folders" but that causes Thunderbird to also show a bunch of Office365 folders that Thunderbird doesn't need, and just creates clutter. I'm having exactly the same problem, as of about 2 days ago. There are no errors in the error console with timestamps at the moment that it disappears. If I Subscribe to a folder, and then restart, the folder appears for a second and then disappears. it shows all the folders as unsubscribed, but if I click Subscribe on them, nothing happens. The only thing in the error console is 6 instances of NS_ERROR_FILE_UNRECOGNIZED_PATH … nsIXPCComponents_Utils.readUTF8URI
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My main home computer is running TB 78.10.2, so I thought maybe it was a version thing, and I backed up all my ImapMail folder and then ran that, and again all folders except Inbox and Deleted Items disappeared. That machine also has Gmail IMAP which has no such problems. Both of those are running TB 52.9.1 (to use the AttachmentExtractor addon). To see if it was just that computer, I tried on a home computer and the same thing happened. I haven't changed any settings or anything, but yesterday I opened Thunderbird on my work computer, and all the folders disappeared except Inbox and Deleted Items. My company email is Office365 and I've been using it through Thunderbird for years with no (serious) problems.
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