If you use an IMAP gmail mail account: When you delete an email, Account Settings should be auto set up to move deleted email to the server gmail trash folder. When I delete a message: select 'Move it to this folder' and choose the subscribed gmail Trash folder on gmail account.

Gmail will auto empty the server Trash folder every 30 days without any intervention from you. When the server/imap Trash folder is emptied, this should delete the original in the 'All Mail' folder. Emails can only be deleted from the 'All Mail' folder if the emails are actually in the gmail Trash folder and it is emptied. You do not delete the emails in the gmail Trash folder - you 'Empty the Trash' folder via a right click or you set Thunderbird up to empty on exit.

You should also compact folders on a regular basis to remove any residual hidden marked as deleted copies from your folders, so they are properly removed. It is a good practise to allow purging of Inbox and emptying of Trash when exiting Thunderbird. This is set up in 'Account Settings' > 'Server Settings'

If you have a POP account then there is no synchronising between pop account folders and gmail server folders, so it is impossible to put deleted emails into the server Trash folder. Hence why it is necessary to access webmail periodically to remove old deleted emails from the 'All Mail' folder.

re :Also when I send a message thunderbird sends 2 copies of the message. Have not found a setting that will prevent this from happening.

There are a few server that have decided to automatically put a copy of any email you send into the server 'Sent' server folder. Gmail does do this.

It sounds like you have also set up Thunderbird to put a copy in the server 'Sent' folder, so now you have two copies.

• 'Account Setting' > Copies & Folders' for gmail account
• Uncheck this checkbox: 'Place a copy in'

then restart Thunderbird.