I then accessed another PC (laptop) where I also have TB loaded, with same folders (although more out of date) & discovered that not only were all my folders missing there, but most of my email addressses too.

I've been using TB for years & this is the first time that I've had a problem like this.

Compunded by the fact that I've just discovered that my profile wasn't included in my back up selection, so if I can't get the folders back, I've lost that information for ever

Thanks

Probably not. for IMAP accounts data is largely a cache then is syncronised to the server, so anything that interrupts the connection can leave the appearance of data loss.

I suggest you try rebooting your computer without your antivirus scanning encrypted connections or email and see if you still even have problem.

Thanks It's all most bizarre. Never had anything like this before & co-incidentally, have just installed the K-9 mail app on my phone.

I thought that once the emails were in a subfolder of local folders, i.e. not in the inbox, they were then stored locally, not via the IMAP server