I have just upgraded a friend’s old 32 bit, 2GB pc to Peppermint 7, after backing up all the data. In particular I backed up the complete ~/.thunderbird and ~/.mozilla directories.
I installed Thunderbird on the new Peppermint system and my intention was to rename the new Thunderbird profile (z8f7bic3.default) to something else and copy the backed-up old one (1fwka4ns.default) to the new system.
I now discover that Thunderbird 52.1.1 has a completely different file structure, but I eventually found that the profile is kept in ~/.cache/thunderbird and I put the old profile in there after renaming the existing default, as above, expecting Thunderbird to pick it up. But it ignored it and simply regenerated its original one, and it turns out that the *.default profiles are also completely different.
I tried using the new Thunderbird’s “Import” feature but it couldn’t find anything to import.
Am I completely screwed? Is there anything I can do? Even installing an earlier version of Thunderbird? Another problem is that I have just travelled 100 miles to visit my friend for this upgrade. Any advice would be appreciated.
I am relieved to discover that although it looked like my friend's old Thunderbird was POP3 it turns out to be IMAP, so all is well! Better than that; she doesn't bother with Local Folders or Address Books, so I'm in the clear (wiping of brow). I feel that this post is not entirely wasted as the new version of Thunderbird may well catch out other unsuspecting users. The moral of this story is to be careful when migrating to the new version, although I'm not sure how one might do that. Perhaps Mozilla have provided a method for doing so, but I haven't found it!