If you have a list of contacts you do not want to ever email via BuzzBuilder, it's helpful to add them to your Opt Out list. Once you've done so, the system will block any users from emailing anyone on this list. Here's how:
From the navigation pane on the left-hand side of the window click on "Opt-Out List"
From this screen, you can either manually input single email addresses to blacklist, or upload a list of emails you wish to be on the blacklist. (Blacklists must be a single sheet CSV with a single header, and column of emails.)
When finished, click "SAVE"