I am unable to permanently delete trash. I am able to "empty trash", however, I noticed an option to "recover deleted items". I do not like this. Items remain since August 2017. I have searched, called support, and tried to recover and delete again. No luck.
The Recovery feature was added some time ago due to the large number of people trying to recover things they later had second thoughts about having deleted. When you delete a message it first goes to Trash where it's kept for 14 days. After that, it gets dumped into the Recover Deleted Items folder, where it will reside for another 15 days. After that, it will drop off and will no longer be recoverable.
Click on the trash folder. Three bars will appear beside it. Click on the bars. One of the options will be "empty trash".
And the messages will still be in the Recovered Deleted Items folder. Also closing a 5 month old thread.