I thought that I had been deleting emails when I sent them to trash and then emptied the trash. Unfortunately it looks like Airmail is somehow archiving ALL email even after it's been deleted. I just found gigabytes of old email that I thought had been permanently deleted. You can test this by doing a search for old email that otherwise should have been deleted. Seriously this is a deal breaker. There MUST be a way to permanently delete email instead of archiving it forever.