Deleting email addresses from Calendar list of invitees

When creating a new calendar invitation and adding invitees, there are email addresses listed there that are NOT recognizable to me and I would like to delete them and prevent them from showing up in the future. How can I delete people from this list? The only option I see is to select email addressed from the list, I do not see ANY feature to delete them PERMANENTLY. I want to remove everyone from the default list but can't see how to do it. Please don't tell me to just delete them, I am looking to clear the default list. Thanks so much for your help!