Is this an imap gmail mail account? If yes, then you need those emails to go into the imap gmail trash bin. Gmail only delete emails that use that gmail trash folder. Otherwise you are only deleting the label not the email; they are still archived in the gmail 'All Mail' folder using up your quota. Gmail auto empty that folder periodically. You can also set up to auto empty the 'Deleted/Trash' folder on exit.

• Right click on imap mail account in Folder Pane and select 'Settings'
• Select 'Server Settings'

Make sure deleted emails are going to gmail imap Trash folder. (I'm presuming you have subscribed to see and use that folder) Otherwise you can select to 'Remove it immediately', but this could present issues as explained - not properly deleted off gmail server.

Message Storage:

• Select checkbox 'Clean up (Expunge) Inbox on delete'
• Select checkbox 'Empty deleted folder on Exit'
• click on 'OK'

Remember, compacting folders especially Inbox, will remove all hidden marked as deleted emails. The 'Expunge' option mentioned above dooes this.

No, my email account is not IMAP. So when a file is deleted by the folder filter, it goes into a local DELETED folder. It seems a problem with Thunderbird, not Gmail.

All Delete actions works that way unless you manually perform the Ctrl Delete as an override action. Therefore filter will auto mark an email as deleted and put it in the Trash for the account.

You can still set up to auto empty the 'Deleted/Trash' folder on exit for pop mail accounts as detailed below, but you may not want your general 'Trash' emptied so quickly as it is offers a means of recovering accidentally deleted emails.

Suggestion: One way of getting around that would be to Create a new folder called something like 'DeleteFiltered' or whatever you want. Then, right click on the 'DeleteFiltered' folder and select 'Properties'. Select 'Retention Policy' tab Here you can choose to override your account settings actions. You could set up this folder to 'Delete messages more than eg:2 days old' and click on 'OK'. These messages are permanently deleted including any originals on the remote server. Then instead of filter action deleting, you perform a move message to that 'DeleteFiltered' folder.

This means you can use two folders for Trash each performing differently.

You can still choose to empty 'Trash' on exit, but it's not so important if you have another folder acting with a different Retention Policy to all other folders.

• Right click on pop mail account in Folder Pane and select 'Settings'
• Select 'Server Settings'

Message Storage:

• Select checkbox 'Empty deleted folder on Exit'
• click on 'OK'

Inbox will still need to be regulary compacted to remove all hidden marked as deleted emails.