OK, giving my inbox a tidy up. I'm using Thunderbird.
I have a folder called 'Wendy'. I sort my e mails by name, select all of them from Wendy and drag them to the 'Wendy' folder.
Now they have vanished!
I've checked the folders either side on the list, plus junk & trash. Nowhere to be seen.
The folder still contains the messages that where already there, but none of the new ones.
Any idea where they have gone?