Archived emails

I don't know where they are archived or which email app you are using but I think you can do the following. Open the folder where they are archived. Press the Command key and the A key to select all of them. The simply execute the delete command as you would normally do. They should be transferred to the Trash. Then you will need to empty the Trash. This will take some time due to the volume of data being deleted. You should reclaim a fair amount of HD storage by doing this, so it's a good thing.