To block an email address, just add to the list with the unsubscribed status. If you want to try to block automated subscriptions, try to activate the antibot options on subscription panel.
You can even create a list of bounced email addresses on a text editor, one per line, and then copy them on subscriber management panel/massive actions, where you can process the full list with a single clic.
Already tried Nearby Photos? Try it and see what’s happening around you!