re :Previously deleted messages went into a "deleted" sub-folder. Use of the word 'Deleted' sounds like a default folder used by a pop mail account, but it would be a top level folder not a sub-folder. Top level folder in the sense that is is directly under the mail account name and not a subfolder to another folder.

re :If I move the message to the trash sub-folder, I delete it from there. Now you mention 'Trash' which could be an imap mail account.

re :Tried recommendations about corrupt trash folder, didn't help. What recommendations? Post link if it helps.

• What Operating System are you using?
• What version of thunderbird?
• Are you talking about a 'pop' or 'imap' mail account?
• Please post image of Folder Pane showing all folders.

I was desperate so I moved all my sub-directories to my gmail account and uninstalled Thunderbird. Cleaned all remnants from my computer then reinstalled. A Lot of work but everything seems to be back to normal.

Still have no idea what caused Thunderbird to mis-behave.

Thanks for offering your help.