I've just downloaded today's Thunderbird update, and it's causing me a BIG and immediate problem. I use four email addresses, each one with its own sub-Inbox, sub-Sentbox etc, and now, while three of the addresses are still there, the first of each of the four sub-inboxes etc - not the emails in them, but the whole sub-inbox etc - has vanished. Also all my archives. It's as though the boxes - for the email address carolinepetherick@gmail.com - never existed. Help, please! (Preferably in words, that I, a moderately techie 74-year-old, should be able to understand.)