Make a backup first.

Please try this: Can you move good emails out of that accounts folders to another folder? If yes, create some folders or use 'Local Folders'.

Starting with mail account Inbox. Move all good emails out of Inbox to eg: Local Folders Inbox. Right click on mail account Inbox and select 'Compact'. Then try to delete one unwanted email. If delete works properly, delete all the rest of those Inbox unwanted emails then repeat: Right click on mail account Inbox and select 'Compact'. then you can move all the Local Folders Inbox emails back to original Inbox.

Repeat doing this on each folder, one at a time.

Why move all those good emails? Because if there is any corruption in the folder, compacting might lose those good emails.

Usually, you do not need to move emails out of folder before compacting. When you delete an email, it gets 'marked as deleted', gets hidden from view and should reappear in 'Deleted/Trash' folder. In reality it is still in the original folder. Compacting removes those 'marked as deleted' emails. I compact my Inbox each day as I delete several emails. The Junk folder also needs compacting after empying.

As an aid, I have the Folder Pane 'Size' column enabled. It tells me the size of the file. So, as an example, if you right click on 'Junk' folder and choose to 'Empty Junk', all the emails disappear but the Size column will show that the size is still the same. Compacting the Junk folder will show the size as empty.

Thanks for the reply, i tried that, no joy.

I have noted something else I have just found, if I right click on the Deleted folder and chose "Empty deleted" it deletes the contents of the Deleted folder, then the folder disappears. When I restart Thunderbird, the Deleted folder is back and so are its contents.

Im at a loss.

Try this;

Make hidden files and folders visible:

• http://kb.mozillazine.org/Show_hidden_files_and_folders

In Thunderbird Help > Troubleshooting Information click on 'show folder' button a new window opens showing the contents of your profile folder name.

Close Thunderbird now - this is important

Look for and delete the following files:

• foldertree.json
• panacea.dat
• session.json

click on 'Mail' folder (assuming this is a pop mail account) click on mail account name that has the issue locate and delete:

• 'Trash' file
• 'Trash.msf' file

Start Thunderbird. All of those files will be recreated.

Please confirm : Is the problem account POP or IMAP ?

Perfect, all fixed! Cheers!

Good to hear all is now working as you would expect.