Ubico lets you suppress emails and/or domains to prevent reaching out to current opportunities or existing customers.
Step 1: Navigate to your account settings.
Step 2: Add domains or emails to your workspace by entering them manually or copy-paste it to the text area. Additionally, you can drop a .csv file that contains the emails or domains. If you're putting more than one domain make sure to separate it with comma, space or new line.
Once saved, these domains will not be contacted and will be used as a suppression list when searching and collecting data for your contacts.