From my old HD (Ubuntu 16.04) I copied ~/.thunderbird
and other programs to the new disk with Ubuntu 18.04 installed.
All went good.
I tried to install Opera. The installation was unsuccessful, a window asking something was held.
After that Thunderbird Local Folders -> Inbox (only) was invaded by large icons like this screenshot
Flowers, plants, trucks and others.
I restarted but those images are still there.
Opera was successfully installed.
What can I do to remove them?